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	$225.60	6.430%	$240.1061	$240.11	$240.10	$240.10
Purchase #2	$180.56	8.601%	$196.09	$196.09	$196.10	$196.10
Purchase #3	$148.74	4.556%	$155.5166	$155.52	$155.50	$155.50
Purchase #4	$42.51	5.460%	$44.831	$44.83	$44.85	$44.80
Purchase #5	$68.82	4.402%	$71.8495	$71.85	$71.85	$71.80
Purchase #6	$96.25	10.648%	$106.4987	$106.50	$106.50	$106.50
Purchase #7	$235.77	6.362%	$250.7697	$250.77	$250.75	$250.80
7 purchase totals =	$998.25		$1,065.6616	$1,065.67	$1,065.65	$1,065.60