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	$57.94	10.451%	$63.9953	$64.00	$64.00	$64.00
Purchase #2	$40.60	11.121%	$45.1151	$45.12	$45.10	$45.10
Purchase #3	$203.87	3.186%	$210.3653	$210.37	$210.35	$210.40
Purchase #4	$38.73	8.286%	$41.9392	$41.94	$41.95	$41.90
Purchase #5	$142.33	11.750%	$159.0538	$159.05	$159.05	$159.10
Purchase #6	$106.94	5.299%	$112.6068	$112.61	$112.60	$112.60
Purchase #7	$95.32	5.718%	$100.7704	$100.77	$100.75	$100.80
7 purchase totals =	$685.73		$733.8459	$733.86	$733.80	$733.90