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	$144.53	7.681%	$155.6313	$155.63	$155.65	$155.60
Purchase #2	$223.78	13.105%	$253.1064	$253.11	$253.10	$253.10
Purchase #3	$61.57	6.271%	$65.4311	$65.43	$65.45	$65.40
Purchase #4	$43.52	8.300%	$47.1322	$47.13	$47.15	$47.10
Purchase #5	$122.98	3.191%	$126.9043	$126.90	$126.90	$126.90
Purchase #6	$80.29	7.686%	$86.4611	$86.46	$86.45	$86.50
Purchase #7	$32.41	7.606%	$34.8751	$34.88	$34.90	$34.90
7 purchase totals =	$709.08		$769.5415	$769.54	$769.60	$769.50