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	$164.51	7.341%	$176.5867	$176.59	$176.60	$176.60
Purchase #2	$206.25	3.381%	$213.2233	$213.22	$213.20	$213.20
Purchase #3	$220.61	4.857%	$231.325	$231.33	$231.35	$231.30
Purchase #4	$58.34	11.625%	$65.122	$65.12	$65.10	$65.10
Purchase #5	$87.63	13.621%	$99.5661	$99.57	$99.55	$99.60
Purchase #6	$62.64	13.376%	$71.0187	$71.02	$71.00	$71.00
Purchase #7	$219.80	10.423%	$242.7098	$242.71	$242.70	$242.70
7 purchase totals =	$1,019.78		$1,099.5516	$1,099.56	$1,099.50	$1,099.50