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	$64.45	12.298%	$72.3761	$72.38	$72.40	$72.40
Purchase #2	$20.95	10.226%	$23.0923	$23.09	$23.10	$23.10
Purchase #3	$203.61	9.771%	$223.5047	$223.50	$223.50	$223.50
Purchase #4	$74.50	11.309%	$82.9252	$82.93	$82.95	$82.90
Purchase #5	$75.69	3.452%	$78.3028	$78.30	$78.30	$78.30
Purchase #6	$205.79	8.216%	$222.6977	$222.70	$222.70	$222.70
Purchase #7	$17.61	9.664%	$19.3118	$19.31	$19.30	$19.30
7 purchase totals =	$662.60		$722.2106	$722.21	$722.25	$722.20