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	$57.98	5.717%	$61.2947	$61.29	$61.30	$61.30
Purchase #2	$231.79	4.871%	$243.0805	$243.08	$243.10	$243.10
Purchase #3	$208.71	7.103%	$223.5347	$223.53	$223.55	$223.50
Purchase #4	$249.62	5.646%	$263.7135	$263.71	$263.70	$263.70
Purchase #5	$99.34	12.676%	$111.9323	$111.93	$111.95	$111.90
Purchase #6	$26.61	9.164%	$29.0485	$29.05	$29.05	$29.00
Purchase #7	$24.73	11.652%	$27.6115	$27.61	$27.60	$27.60
7 purchase totals =	$898.78		$960.2157	$960.20	$960.25	$960.10