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	$94.61	4.801%	$99.1522	$99.15	$99.15	$99.20
Purchase #2	$170.84	11.619%	$190.6899	$190.69	$190.70	$190.70
Purchase #3	$199.93	7.171%	$214.267	$214.27	$214.25	$214.30
Purchase #4	$122.82	4.460%	$128.2978	$128.30	$128.30	$128.30
Purchase #5	$201.41	12.512%	$226.6104	$226.61	$226.60	$226.60
Purchase #6	$33.89	4.767%	$35.5055	$35.51	$35.50	$35.50
Purchase #7	$131.33	10.183%	$144.7033	$144.70	$144.70	$144.70
7 purchase totals =	$954.83		$1,039.2261	$1,039.23	$1,039.20	$1,039.30