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	$21.66	4.849%	$22.7103	$22.71	$22.70	$22.70
Purchase #2	$248.53	6.598%	$264.928	$264.93	$264.95	$264.90
Purchase #3	$47.37	12.537%	$53.3088	$53.31	$53.30	$53.30
Purchase #4	$54.81	5.124%	$57.6185	$57.62	$57.60	$57.60
Purchase #5	$218.83	12.274%	$245.6892	$245.69	$245.70	$245.70
Purchase #6	$102.89	8.732%	$111.8744	$111.87	$111.85	$111.90
Purchase #7	$5.33	11.502%	$5.9431	$5.94	$5.95	$5.90
7 purchase totals =	$699.42		$762.0723	$762.07	$762.05	$762.00