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	$91.57	7.563%	$98.4954	$98.50	$98.50	$98.50
Purchase #2	$74.55	4.787%	$78.1187	$78.12	$78.10	$78.10
Purchase #3	$138.81	10.153%	$152.9034	$152.90	$152.90	$152.90
Purchase #4	$64.80	3.649%	$67.1646	$67.16	$67.15	$67.20
Purchase #5	$119.79	8.258%	$129.6823	$129.68	$129.70	$129.70
Purchase #6	$248.78	3.277%	$256.9325	$256.93	$256.95	$256.90
Purchase #7	$36.94	9.164%	$40.3252	$40.33	$40.35	$40.30
7 purchase totals =	$775.24		$823.6221	$823.62	$823.65	$823.60