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	$46.76	12.554%	$52.6303	$52.63	$52.65	$52.60
Purchase #2	$110.78	12.131%	$124.2187	$124.22	$124.20	$124.20
Purchase #3	$59.48	13.780%	$67.6763	$67.68	$67.70	$67.70
Purchase #4	$59.85	3.565%	$61.9837	$61.98	$62.00	$62.00
Purchase #5	$156.78	8.504%	$170.1126	$170.11	$170.10	$170.10
Purchase #6	$121.71	7.314%	$130.6119	$130.61	$130.60	$130.60
Purchase #7	$83.79	9.844%	$92.0383	$92.04	$92.05	$92.00
7 purchase totals =	$639.15		$699.2718	$699.27	$699.30	$699.20