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	$142.31	4.868%	$149.2377	$149.24	$149.25	$149.20
Purchase #2	$94.30	11.114%	$104.7805	$104.78	$104.80	$104.80
Purchase #3	$205.43	13.112%	$232.366	$232.37	$232.35	$232.40
Purchase #4	$182.68	8.132%	$197.5355	$197.54	$197.55	$197.50
Purchase #5	$181.37	4.847%	$190.161	$190.16	$190.15	$190.20
Purchase #6	$37.59	8.772%	$40.8874	$40.89	$40.90	$40.90
Purchase #7	$64.27	12.732%	$72.4529	$72.45	$72.45	$72.50
7 purchase totals =	$907.95		$987.4210	$987.43	$987.45	$987.50