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	$237.92	4.351%	$248.2719	$248.27	$248.25	$248.30
Purchase #2	$118.85	4.497%	$124.1947	$124.19	$124.20	$124.20
Purchase #3	$141.75	10.801%	$157.0604	$157.06	$157.05	$157.10
Purchase #4	$126.55	3.179%	$130.573	$130.57	$130.55	$130.60
Purchase #5	$200.27	9.646%	$219.588	$219.59	$219.60	$219.60
Purchase #6	$100.71	10.248%	$111.0308	$111.03	$111.05	$111.00
Purchase #7	$11.76	6.795%	$12.5591	$12.56	$12.55	$12.60
7 purchase totals =	$937.81		$1,003.2779	$1,003.27	$1,003.25	$1,003.40