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	$53.52	4.319%	$55.8315	$55.83	$55.85	$55.80
Purchase #2	$99.32	5.841%	$105.1213	$105.12	$105.10	$105.10
Purchase #3	$204.63	3.504%	$211.8002	$211.80	$211.80	$211.80
Purchase #4	$54.96	10.760%	$60.8737	$60.87	$60.85	$60.90
Purchase #5	$243.77	3.808%	$253.0528	$253.05	$253.05	$253.10
Purchase #6	$71.47	13.121%	$80.8476	$80.85	$80.85	$80.80
Purchase #7	$141.92	11.261%	$157.9016	$157.90	$157.90	$157.90
7 purchase totals =	$869.59		$925.4287	$925.42	$925.40	$925.40