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	$191.75	6.705%	$204.6068	$204.61	$204.60	$204.60
Purchase #2	$236.63	6.319%	$251.5826	$251.58	$251.60	$251.60
Purchase #3	$190.53	9.688%	$208.9885	$208.99	$209.00	$209.00
Purchase #4	$237.79	6.516%	$253.2844	$253.28	$253.30	$253.30
Purchase #5	$223.64	11.874%	$250.195	$250.20	$250.20	$250.20
Purchase #6	$186.59	5.324%	$196.5241	$196.52	$196.50	$196.50
Purchase #7	$103.39	7.742%	$111.3945	$111.39	$111.40	$111.40
7 purchase totals =	$1,370.32		$1,476.5759	$1,476.57	$1,476.60	$1,476.60