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	$238.25	6.593%	$253.9578	$253.96	$253.95	$254.00
Purchase #2	$134.89	12.738%	$152.0723	$152.07	$152.05	$152.10
Purchase #3	$202.89	9.652%	$222.4729	$222.47	$222.45	$222.50
Purchase #4	$167.49	10.391%	$184.8939	$184.89	$184.90	$184.90
Purchase #5	$54.79	6.729%	$58.4768	$58.48	$58.50	$58.50
Purchase #6	$194.83	13.668%	$221.4594	$221.46	$221.45	$221.50
Purchase #7	$152.96	8.857%	$166.5077	$166.51	$166.50	$166.50
7 purchase totals =	$1,146.10		$1,259.8408	$1,259.84	$1,259.80	$1,260.00