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	$164.28	6.852%	$175.5365	$175.54	$175.55	$175.50
Purchase #2	$191.66	7.575%	$206.1782	$206.18	$206.20	$206.20
Purchase #3	$87.70	6.386%	$93.3005	$93.30	$93.30	$93.30
Purchase #4	$68.55	5.869%	$72.5732	$72.57	$72.55	$72.60
Purchase #5	$70.56	11.711%	$78.8233	$78.82	$78.80	$78.80
Purchase #6	$48.86	5.167%	$51.3846	$51.38	$51.40	$51.40
Purchase #7	$88.35	3.569%	$91.5032	$91.50	$91.50	$91.50
7 purchase totals =	$719.96		$769.2995	$769.29	$769.30	$769.30