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	$168.43	12.345%	$189.2227	$189.22	$189.20	$189.20
Purchase #2	$79.89	13.235%	$90.4634	$90.46	$90.45	$90.50
Purchase #3	$17.92	6.569%	$19.0972	$19.10	$19.10	$19.10
Purchase #4	$180.72	6.847%	$193.0939	$193.09	$193.10	$193.10
Purchase #5	$202.72	13.772%	$230.6386	$230.64	$230.65	$230.60
Purchase #6	$109.46	6.387%	$116.4512	$116.45	$116.45	$116.50
Purchase #7	$91.59	11.742%	$102.3445	$102.34	$102.35	$102.30
7 purchase totals =	$850.73		$941.3115	$941.30	$941.30	$941.30