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	$197.31	5.363%	$207.8917	$207.89	$207.90	$207.90
Purchase #2	$208.95	6.473%	$222.4753	$222.48	$222.50	$222.50
Purchase #3	$233.58	7.260%	$250.5379	$250.54	$250.55	$250.50
Purchase #4	$83.37	8.173%	$90.1838	$90.18	$90.20	$90.20
Purchase #5	$147.96	5.692%	$156.3819	$156.38	$156.40	$156.40
Purchase #6	$68.39	11.341%	$76.1461	$76.15	$76.15	$76.10
Purchase #7	$111.25	4.379%	$116.1216	$116.12	$116.10	$116.10
7 purchase totals =	$1,050.81		$1,119.7383	$1,119.74	$1,119.80	$1,119.70