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	$200.97	13.200%	$227.498	$227.50	$227.50	$227.50
Purchase #2	$242.53	5.674%	$256.2912	$256.29	$256.30	$256.30
Purchase #3	$37.38	11.635%	$41.7292	$41.73	$41.75	$41.70
Purchase #4	$51.39	3.350%	$53.1116	$53.11	$53.10	$53.10
Purchase #5	$168.52	13.143%	$190.6686	$190.67	$190.65	$190.70
Purchase #6	$188.72	4.231%	$196.7047	$196.70	$196.70	$196.70
Purchase #7	$206.36	5.346%	$217.392	$217.39	$217.40	$217.40
7 purchase totals =	$1,095.87		$1,183.3953	$1,183.39	$1,183.40	$1,183.40