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	$42.33	10.724%	$46.8695	$46.87	$46.85	$46.90
Purchase #2	$105.32	6.188%	$111.8372	$111.84	$111.85	$111.80
Purchase #3	$89.29	7.618%	$96.0921	$96.09	$96.10	$96.10
Purchase #4	$32.57	11.168%	$36.2074	$36.21	$36.20	$36.20
Purchase #5	$207.94	8.262%	$225.12	$225.12	$225.10	$225.10
Purchase #6	$162.36	5.749%	$171.6941	$171.69	$171.70	$171.70
Purchase #7	$20.87	8.290%	$22.6001	$22.60	$22.60	$22.60
7 purchase totals =	$660.68		$710.4204	$710.42	$710.40	$710.40