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	$173.41	11.140%	$192.7279	$192.73	$192.75	$192.70
Purchase #2	$80.73	5.374%	$85.0684	$85.07	$85.05	$85.10
Purchase #3	$170.59	6.310%	$181.3542	$181.35	$181.35	$181.40
Purchase #4	$104.78	5.553%	$110.5984	$110.60	$110.60	$110.60
Purchase #5	$38.89	9.513%	$42.5896	$42.59	$42.60	$42.60
Purchase #6	$57.54	5.754%	$60.8509	$60.85	$60.85	$60.90
Purchase #7	$124.27	9.548%	$136.1353	$136.14	$136.15	$136.10
7 purchase totals =	$750.21		$809.3247	$809.33	$809.35	$809.40