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	$132.43	13.118%	$149.8022	$149.80	$149.80	$149.80
Purchase #2	$94.42	6.635%	$100.6848	$100.68	$100.70	$100.70
Purchase #3	$181.33	13.439%	$205.6989	$205.70	$205.70	$205.70
Purchase #4	$100.98	7.574%	$108.6282	$108.63	$108.65	$108.60
Purchase #5	$200.72	3.771%	$208.2892	$208.29	$208.30	$208.30
Purchase #6	$198.38	5.626%	$209.5409	$209.54	$209.55	$209.50
Purchase #7	$176.69	11.348%	$196.7408	$196.74	$196.75	$196.70
7 purchase totals =	$1,084.95		$1,179.3850	$1,179.38	$1,179.45	$1,179.30