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	$120.91	8.723%	$131.457	$131.46	$131.45	$131.50
Purchase #2	$18.45	9.399%	$20.1841	$20.18	$20.20	$20.20
Purchase #3	$139.89	8.575%	$151.8856	$151.89	$151.90	$151.90
Purchase #4	$100.63	8.369%	$109.0517	$109.05	$109.05	$109.10
Purchase #5	$163.44	5.824%	$172.9587	$172.96	$172.95	$173.00
Purchase #6	$116.70	8.634%	$126.7759	$126.78	$126.80	$126.80
Purchase #7	$216.31	6.550%	$230.4783	$230.48	$230.50	$230.50
7 purchase totals =	$876.33		$942.7913	$942.80	$942.85	$943.00