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	$153.68	11.874%	$171.928	$171.93	$171.95	$171.90
Purchase #2	$93.45	7.404%	$100.369	$100.37	$100.35	$100.40
Purchase #3	$6.83	4.133%	$7.1123	$7.11	$7.10	$7.10
Purchase #4	$177.54	7.112%	$190.1666	$190.17	$190.15	$190.20
Purchase #5	$61.28	10.460%	$67.6899	$67.69	$67.70	$67.70
Purchase #6	$85.48	11.189%	$95.0444	$95.04	$95.05	$95.00
Purchase #7	$172.75	4.559%	$180.6257	$180.63	$180.65	$180.60
7 purchase totals =	$751.01		$812.9359	$812.94	$812.95	$812.90