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	$170.78	11.461%	$190.3531	$190.35	$190.35	$190.40
Purchase #2	$50.72	6.874%	$54.2065	$54.21	$54.20	$54.20
Purchase #3	$210.74	8.662%	$228.9943	$228.99	$229.00	$229.00
Purchase #4	$64.89	9.838%	$71.2739	$71.27	$71.25	$71.30
Purchase #5	$228.42	12.115%	$256.0931	$256.09	$256.10	$256.10
Purchase #6	$169.25	6.809%	$180.7742	$180.77	$180.75	$180.80
Purchase #7	$95.78	8.563%	$103.9816	$103.98	$104.00	$104.00
7 purchase totals =	$990.58		$1,085.6767	$1,085.66	$1,085.65	$1,085.80