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	$57.96	7.357%	$62.2241	$62.22	$62.20	$62.20
Purchase #2	$184.37	8.162%	$199.4183	$199.42	$199.40	$199.40
Purchase #3	$25.44	5.711%	$26.8929	$26.89	$26.90	$26.90
Purchase #4	$40.50	7.830%	$43.6712	$43.67	$43.65	$43.70
Purchase #5	$133.27	11.536%	$148.644	$148.64	$148.65	$148.60
Purchase #6	$210.40	5.708%	$222.4096	$222.41	$222.40	$222.40
Purchase #7	$198.94	11.742%	$222.2995	$222.30	$222.30	$222.30
7 purchase totals =	$850.88		$925.5596	$925.55	$925.50	$925.50