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	$196.59	11.641%	$219.475	$219.48	$219.50	$219.50
Purchase #2	$206.39	7.847%	$222.5854	$222.59	$222.60	$222.60
Purchase #3	$89.60	4.691%	$93.8031	$93.80	$93.80	$93.80
Purchase #4	$99.50	6.843%	$106.3088	$106.31	$106.30	$106.30
Purchase #5	$87.65	12.643%	$98.7316	$98.73	$98.75	$98.70
Purchase #6	$195.90	8.322%	$212.2028	$212.20	$212.20	$212.20
Purchase #7	$48.54	7.717%	$52.2858	$52.29	$52.30	$52.30
7 purchase totals =	$924.17		$1,005.3925	$1,005.40	$1,005.45	$1,005.40