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	$157.59	10.488%	$174.118	$174.12	$174.10	$174.10
Purchase #2	$80.34	9.663%	$88.1033	$88.10	$88.10	$88.10
Purchase #3	$170.98	7.692%	$184.1318	$184.13	$184.15	$184.10
Purchase #4	$30.89	5.809%	$32.6844	$32.68	$32.70	$32.70
Purchase #5	$101.81	10.297%	$112.2934	$112.29	$112.30	$112.30
Purchase #6	$136.56	4.585%	$142.8213	$142.82	$142.80	$142.80
Purchase #7	$221.64	9.433%	$242.5473	$242.55	$242.55	$242.50
7 purchase totals =	$899.81		$976.6995	$976.69	$976.70	$976.60