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	$101.90	4.797%	$106.7881	$106.79	$106.80	$106.80
Purchase #2	$240.95	10.234%	$265.6088	$265.61	$265.60	$265.60
Purchase #3	$230.62	10.729%	$255.3632	$255.36	$255.35	$255.40
Purchase #4	$80.90	10.417%	$89.3274	$89.33	$89.35	$89.30
Purchase #5	$93.27	3.846%	$96.8572	$96.86	$96.85	$96.90
Purchase #6	$51.45	13.131%	$58.2059	$58.21	$58.20	$58.20
Purchase #7	$12.89	12.530%	$14.5051	$14.51	$14.50	$14.50
7 purchase totals =	$811.98		$886.6557	$886.67	$886.65	$886.70