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	$97.81	7.569%	$105.2132	$105.21	$105.20	$105.20
Purchase #2	$12.91	5.340%	$13.5994	$13.60	$13.60	$13.60
Purchase #3	$210.45	4.354%	$219.613	$219.61	$219.60	$219.60
Purchase #4	$64.58	7.180%	$69.2168	$69.22	$69.20	$69.20
Purchase #5	$169.90	11.116%	$188.7861	$188.79	$188.80	$188.80
Purchase #6	$100.52	10.855%	$111.4314	$111.43	$111.45	$111.40
Purchase #7	$67.69	13.587%	$76.887	$76.89	$76.90	$76.90
7 purchase totals =	$723.86		$784.7469	$784.75	$784.75	$784.70