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	$177.85	7.157%	$190.5787	$190.58	$190.60	$190.60
Purchase #2	$63.48	12.802%	$71.6067	$71.61	$71.60	$71.60
Purchase #3	$18.54	12.309%	$20.8221	$20.82	$20.80	$20.80
Purchase #4	$223.62	11.393%	$249.097	$249.10	$249.10	$249.10
Purchase #5	$37.76	7.836%	$40.7189	$40.72	$40.70	$40.70
Purchase #6	$101.71	13.584%	$115.5263	$115.53	$115.55	$115.50
Purchase #7	$69.29	6.650%	$73.8978	$73.90	$73.90	$73.90
7 purchase totals =	$692.25		$762.2475	$762.26	$762.25	$762.20