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	$140.54	8.333%	$152.2512	$152.25	$152.25	$152.30
Purchase #2	$194.82	5.296%	$205.1377	$205.14	$205.15	$205.10
Purchase #3	$208.69	4.535%	$218.1541	$218.15	$218.15	$218.20
Purchase #4	$148.51	4.390%	$155.0296	$155.03	$155.05	$155.00
Purchase #5	$53.76	9.167%	$58.6882	$58.69	$58.70	$58.70
Purchase #6	$32.59	13.226%	$36.9004	$36.90	$36.90	$36.90
Purchase #7	$233.62	9.396%	$255.5709	$255.57	$255.55	$255.60
7 purchase totals =	$1,012.53		$1,081.7321	$1,081.73	$1,081.75	$1,081.80