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	$64.27	5.142%	$67.5748	$67.57	$67.55	$67.60
Purchase #2	$59.85	3.105%	$61.7083	$61.71	$61.70	$61.70
Purchase #3	$100.79	3.818%	$104.6382	$104.64	$104.65	$104.60
Purchase #4	$29.54	5.426%	$31.1428	$31.14	$31.15	$31.10
Purchase #5	$152.30	12.783%	$171.7685	$171.77	$171.75	$171.80
Purchase #6	$217.66	5.269%	$229.1285	$229.13	$229.15	$229.10
Purchase #7	$25.27	7.202%	$27.0899	$27.09	$27.10	$27.10
7 purchase totals =	$649.68		$693.0510	$693.05	$693.05	$693.00