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	$56.37	13.385%	$63.9151	$63.92	$63.90	$63.90
Purchase #2	$234.91	7.418%	$252.3356	$252.34	$252.35	$252.30
Purchase #3	$181.86	10.174%	$200.3624	$200.36	$200.35	$200.40
Purchase #4	$194.69	13.369%	$220.7181	$220.72	$220.70	$220.70
Purchase #5	$37.84	11.680%	$42.2597	$42.26	$42.25	$42.30
Purchase #6	$160.96	5.344%	$169.5617	$169.56	$169.55	$169.60
Purchase #7	$96.74	3.443%	$100.0708	$100.07	$100.05	$100.10
7 purchase totals =	$963.37		$1,049.2234	$1,049.23	$1,049.15	$1,049.30