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	$48.41	13.865%	$55.122	$55.12	$55.10	$55.10
Purchase #2	$25.51	12.644%	$28.7355	$28.74	$28.75	$28.70
Purchase #3	$226.81	7.251%	$243.256	$243.26	$243.25	$243.30
Purchase #4	$141.89	11.825%	$158.6685	$158.67	$158.65	$158.70
Purchase #5	$140.47	3.737%	$145.7194	$145.72	$145.70	$145.70
Purchase #6	$134.83	11.604%	$150.4757	$150.48	$150.50	$150.50
Purchase #7	$74.85	11.674%	$83.588	$83.59	$83.60	$83.60
7 purchase totals =	$792.77		$865.5651	$865.58	$865.55	$865.60