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	$124.50	10.756%	$137.8912	$137.89	$137.90	$137.90
Purchase #2	$195.52	11.182%	$217.383	$217.38	$217.40	$217.40
Purchase #3	$182.63	11.763%	$204.1128	$204.11	$204.10	$204.10
Purchase #4	$242.25	5.349%	$255.208	$255.21	$255.20	$255.20
Purchase #5	$52.47	10.282%	$57.865	$57.87	$57.85	$57.90
Purchase #6	$183.91	6.383%	$195.649	$195.65	$195.65	$195.60
Purchase #7	$123.73	3.805%	$128.4379	$128.44	$128.45	$128.40
7 purchase totals =	$1,105.01		$1,196.5469	$1,196.55	$1,196.55	$1,196.50