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	$110.87	12.654%	$124.8995	$124.90	$124.90	$124.90
Purchase #2	$84.97	7.271%	$91.1482	$91.15	$91.15	$91.10
Purchase #3	$105.33	10.301%	$116.18	$116.18	$116.20	$116.20
Purchase #4	$44.72	12.806%	$50.4468	$50.45	$50.45	$50.40
Purchase #5	$38.93	5.645%	$41.1276	$41.13	$41.15	$41.10
Purchase #6	$125.55	5.632%	$132.621	$132.62	$132.60	$132.60
Purchase #7	$42.30	6.532%	$45.063	$45.06	$45.05	$45.10
7 purchase totals =	$552.67		$601.4861	$601.49	$601.50	$601.40