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	$216.98	13.477%	$246.2224	$246.22	$246.20	$246.20
Purchase #2	$41.80	9.437%	$45.7447	$45.74	$45.75	$45.70
Purchase #3	$152.54	5.794%	$161.3782	$161.38	$161.40	$161.40
Purchase #4	$29.89	12.633%	$33.666	$33.67	$33.65	$33.70
Purchase #5	$153.38	9.395%	$167.7901	$167.79	$167.80	$167.80
Purchase #6	$83.33	7.176%	$89.3098	$89.31	$89.30	$89.30
Purchase #7	$199.53	3.450%	$206.4138	$206.41	$206.40	$206.40
7 purchase totals =	$877.45		$950.5250	$950.52	$950.50	$950.50