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	$89.90	11.372%	$100.1234	$100.12	$100.10	$100.10
Purchase #2	$116.34	7.405%	$124.955	$124.96	$124.95	$125.00
Purchase #3	$148.28	11.788%	$165.7592	$165.76	$165.75	$165.80
Purchase #4	$247.70	11.388%	$275.9081	$275.91	$275.90	$275.90
Purchase #5	$36.92	8.299%	$39.984	$39.98	$40.00	$40.00
Purchase #6	$57.38	13.570%	$65.1665	$65.17	$65.15	$65.20
Purchase #7	$217.29	12.132%	$243.6516	$243.65	$243.65	$243.70
7 purchase totals =	$913.81		$1,015.5478	$1,015.55	$1,015.50	$1,015.70