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	$211.42	8.138%	$228.6254	$228.63	$228.65	$228.60
Purchase #2	$69.92	12.396%	$78.5873	$78.59	$78.60	$78.60
Purchase #3	$176.45	6.815%	$188.4751	$188.48	$188.50	$188.50
Purchase #4	$40.70	9.317%	$44.492	$44.49	$44.50	$44.50
Purchase #5	$54.99	13.530%	$62.4301	$62.43	$62.45	$62.40
Purchase #6	$244.35	4.634%	$255.6732	$255.67	$255.65	$255.70
Purchase #7	$36.96	11.854%	$41.3412	$41.34	$41.35	$41.30
7 purchase totals =	$834.79		$899.6243	$899.63	$899.70	$899.60