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	$244.29	5.639%	$258.0655	$258.07	$258.05	$258.10
Purchase #2	$53.88	4.171%	$56.1273	$56.13	$56.15	$56.10
Purchase #3	$147.43	9.443%	$161.3518	$161.35	$161.35	$161.40
Purchase #4	$179.41	4.487%	$187.4601	$187.46	$187.45	$187.50
Purchase #5	$91.94	13.626%	$104.4677	$104.47	$104.45	$104.50
Purchase #6	$153.93	11.835%	$172.1476	$172.15	$172.15	$172.10
Purchase #7	$147.77	3.211%	$152.5149	$152.51	$152.50	$152.50
7 purchase totals =	$1,018.65		$1,092.1349	$1,092.14	$1,092.10	$1,092.20