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	$223.43	10.425%	$246.7226	$246.72	$246.70	$246.70
Purchase #2	$131.69	13.172%	$149.0362	$149.04	$149.05	$149.00
Purchase #3	$72.77	8.130%	$78.6862	$78.69	$78.70	$78.70
Purchase #4	$105.76	3.392%	$109.3474	$109.35	$109.35	$109.30
Purchase #5	$7.27	5.756%	$7.6885	$7.69	$7.70	$7.70
Purchase #6	$194.55	5.343%	$204.9448	$204.94	$204.95	$204.90
Purchase #7	$121.36	8.425%	$131.5846	$131.58	$131.60	$131.60
7 purchase totals =	$856.83		$928.0103	$928.01	$928.05	$927.90