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	$40.89	4.801%	$42.8531	$42.85	$42.85	$42.90
Purchase #2	$23.58	10.213%	$25.9882	$25.99	$26.00	$26.00
Purchase #3	$243.39	8.517%	$264.1195	$264.12	$264.10	$264.10
Purchase #4	$6.67	10.224%	$7.3519	$7.35	$7.35	$7.40
Purchase #5	$36.64	3.472%	$37.9121	$37.91	$37.90	$37.90
Purchase #6	$145.76	11.292%	$162.2192	$162.22	$162.20	$162.20
Purchase #7	$209.29	9.439%	$229.0449	$229.04	$229.05	$229.00
7 purchase totals =	$706.22		$769.4889	$769.48	$769.45	$769.50