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	$9.64	4.872%	$10.1097	$10.11	$10.10	$10.10
Purchase #2	$219.33	10.119%	$241.524	$241.52	$241.50	$241.50
Purchase #3	$227.97	11.868%	$255.0255	$255.03	$255.05	$255.00
Purchase #4	$232.34	6.804%	$248.1484	$248.15	$248.15	$248.10
Purchase #5	$79.67	13.569%	$90.4804	$90.48	$90.50	$90.50
Purchase #6	$65.70	10.438%	$72.5578	$72.56	$72.55	$72.60
Purchase #7	$217.55	13.855%	$247.6916	$247.69	$247.70	$247.70
7 purchase totals =	$1,052.20		$1,165.5374	$1,165.54	$1,165.55	$1,165.50