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	$55.79	12.504%	$62.766	$62.77	$62.75	$62.80
Purchase #2	$89.30	6.153%	$94.7946	$94.79	$94.80	$94.80
Purchase #3	$206.83	8.809%	$225.0497	$225.05	$225.05	$225.00
Purchase #4	$57.67	8.175%	$62.3845	$62.38	$62.40	$62.40
Purchase #5	$16.76	10.804%	$18.5708	$18.57	$18.55	$18.60
Purchase #6	$212.50	5.388%	$223.9495	$223.95	$223.95	$223.90
Purchase #7	$101.25	4.113%	$105.4144	$105.41	$105.40	$105.40
7 purchase totals =	$740.10		$792.9295	$792.92	$792.90	$792.90