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	$192.70	9.849%	$211.679	$211.68	$211.70	$211.70
Purchase #2	$243.89	8.460%	$264.5231	$264.52	$264.50	$264.50
Purchase #3	$136.25	4.736%	$142.7028	$142.70	$142.70	$142.70
Purchase #4	$238.62	11.218%	$265.3884	$265.39	$265.40	$265.40
Purchase #5	$126.77	13.322%	$143.6583	$143.66	$143.65	$143.70
Purchase #6	$61.57	8.446%	$66.7702	$66.77	$66.75	$66.80
Purchase #7	$104.92	6.539%	$111.7807	$111.78	$111.80	$111.80
7 purchase totals =	$1,104.72		$1,206.5025	$1,206.50	$1,206.50	$1,206.60