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	$245.67	4.442%	$256.5827	$256.58	$256.60	$256.60
Purchase #2	$75.59	3.538%	$78.2644	$78.26	$78.25	$78.30
Purchase #3	$234.62	4.203%	$244.4811	$244.48	$244.50	$244.50
Purchase #4	$148.77	11.166%	$165.3817	$165.38	$165.40	$165.40
Purchase #5	$32.96	9.743%	$36.1713	$36.17	$36.15	$36.20
Purchase #6	$127.27	10.514%	$140.6512	$140.65	$140.65	$140.70
Purchase #7	$155.99	5.446%	$164.4852	$164.49	$164.50	$164.50
7 purchase totals =	$1,020.87		$1,086.0176	$1,086.01	$1,086.05	$1,086.20