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	$133.93	9.558%	$146.731	$146.73	$146.75	$146.70
Purchase #2	$40.46	6.584%	$43.1239	$43.12	$43.10	$43.10
Purchase #3	$139.88	6.357%	$148.7722	$148.77	$148.75	$148.80
Purchase #4	$137.84	5.104%	$144.8754	$144.88	$144.90	$144.90
Purchase #5	$43.25	8.374%	$46.8718	$46.87	$46.85	$46.90
Purchase #6	$64.51	10.864%	$71.5184	$71.52	$71.50	$71.50
Purchase #7	$109.67	8.211%	$118.675	$118.68	$118.70	$118.70
7 purchase totals =	$669.54		$720.5677	$720.57	$720.55	$720.60