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	$145.83	3.477%	$150.9005	$150.90	$150.90	$150.90
Purchase #2	$118.47	7.287%	$127.1029	$127.10	$127.10	$127.10
Purchase #3	$199.44	4.281%	$207.978	$207.98	$208.00	$208.00
Purchase #4	$74.78	12.148%	$83.8643	$83.86	$83.85	$83.90
Purchase #5	$88.32	10.293%	$97.4108	$97.41	$97.40	$97.40
Purchase #6	$9.30	3.499%	$9.6254	$9.63	$9.65	$9.60
Purchase #7	$124.46	4.766%	$130.3918	$130.39	$130.40	$130.40
7 purchase totals =	$760.60		$807.2737	$807.27	$807.30	$807.30