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	$67.41	13.593%	$76.573	$76.57	$76.55	$76.60
Purchase #2	$55.94	11.784%	$62.532	$62.53	$62.55	$62.50
Purchase #3	$202.61	12.421%	$227.7762	$227.78	$227.80	$227.80
Purchase #4	$192.32	3.196%	$198.4665	$198.47	$198.45	$198.50
Purchase #5	$56.25	5.326%	$59.2459	$59.25	$59.25	$59.20
Purchase #6	$127.49	11.784%	$142.5134	$142.51	$142.50	$142.50
Purchase #7	$235.77	8.810%	$256.5413	$256.54	$256.55	$256.50
7 purchase totals =	$937.79		$1,023.6483	$1,023.65	$1,023.65	$1,023.60