Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.34	3.368%	$153.3361	$153.34	$153.35	$153.30
Purchase #2	$171.26	9.812%	$188.064	$188.06	$188.05	$188.10
Purchase #3	$186.99	5.166%	$196.6499	$196.65	$196.65	$196.60
Purchase #4	$138.73	11.349%	$154.4745	$154.47	$154.45	$154.50
Purchase #5	$149.48	10.213%	$164.7464	$164.75	$164.75	$164.70
Purchase #6	$119.50	3.292%	$123.4339	$123.43	$123.45	$123.40
Purchase #7	$101.29	6.414%	$107.7867	$107.79	$107.80	$107.80
7 purchase totals =	$1,015.59		$1,088.4915	$1,088.49	$1,088.50	$1,088.40