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	$51.66	7.460%	$55.5138	$55.51	$55.50	$55.50
Purchase #2	$107.86	7.864%	$116.3421	$116.34	$116.35	$116.30
Purchase #3	$67.73	5.869%	$71.7051	$71.71	$71.70	$71.70
Purchase #4	$29.31	11.566%	$32.7	$32.70	$32.70	$32.70
Purchase #5	$200.33	4.755%	$209.8557	$209.86	$209.85	$209.90
Purchase #6	$155.38	11.112%	$172.6458	$172.65	$172.65	$172.60
Purchase #7	$226.30	8.623%	$245.8138	$245.81	$245.80	$245.80
7 purchase totals =	$838.57		$904.5763	$904.58	$904.55	$904.50