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	$157.56	10.398%	$173.9431	$173.94	$173.95	$173.90
Purchase #2	$43.71	3.261%	$45.1354	$45.14	$45.15	$45.10
Purchase #3	$85.89	3.395%	$88.806	$88.81	$88.80	$88.80
Purchase #4	$84.62	5.777%	$89.5085	$89.51	$89.50	$89.50
Purchase #5	$190.45	11.784%	$212.8926	$212.89	$212.90	$212.90
Purchase #6	$101.57	13.384%	$115.1641	$115.16	$115.15	$115.20
Purchase #7	$192.93	10.643%	$213.4635	$213.46	$213.45	$213.50
7 purchase totals =	$856.73		$938.9132	$938.91	$938.90	$938.90