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	$216.52	11.820%	$242.1127	$242.11	$242.10	$242.10
Purchase #2	$164.29	7.301%	$176.2848	$176.28	$176.30	$176.30
Purchase #3	$40.68	3.321%	$42.031	$42.03	$42.05	$42.00
Purchase #4	$189.34	3.833%	$196.5974	$196.60	$196.60	$196.60
Purchase #5	$125.91	12.615%	$141.7935	$141.79	$141.80	$141.80
Purchase #6	$151.49	4.840%	$158.8221	$158.82	$158.80	$158.80
Purchase #7	$203.28	11.441%	$226.5373	$226.54	$226.55	$226.50
7 purchase totals =	$1,091.51		$1,184.1788	$1,184.17	$1,184.20	$1,184.10