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	$140.43	4.194%	$146.3196	$146.32	$146.30	$146.30
Purchase #2	$94.99	5.393%	$100.1128	$100.11	$100.10	$100.10
Purchase #3	$214.89	13.238%	$243.3371	$243.34	$243.35	$243.30
Purchase #4	$222.82	5.806%	$235.7569	$235.76	$235.75	$235.80
Purchase #5	$84.92	11.142%	$94.3818	$94.38	$94.40	$94.40
Purchase #6	$96.39	13.325%	$109.234	$109.23	$109.25	$109.20
Purchase #7	$233.55	13.846%	$265.8873	$265.89	$265.90	$265.90
7 purchase totals =	$1,087.99		$1,195.0295	$1,195.03	$1,195.05	$1,195.00