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	$157.91	10.413%	$174.3532	$174.35	$174.35	$174.40
Purchase #2	$16.27	13.652%	$18.4912	$18.49	$18.50	$18.50
Purchase #3	$45.82	5.872%	$48.5106	$48.51	$48.50	$48.50
Purchase #4	$7.58	10.550%	$8.3797	$8.38	$8.40	$8.40
Purchase #5	$59.37	4.237%	$61.8855	$61.89	$61.90	$61.90
Purchase #6	$127.36	12.759%	$143.6099	$143.61	$143.60	$143.60
Purchase #7	$105.57	10.270%	$116.412	$116.41	$116.40	$116.40
7 purchase totals =	$519.88		$571.6421	$571.64	$571.65	$571.70