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	$175.95	6.279%	$186.9979	$187.00	$187.00	$187.00
Purchase #2	$10.38	5.316%	$10.9318	$10.93	$10.95	$10.90
Purchase #3	$118.76	11.755%	$132.7202	$132.72	$132.70	$132.70
Purchase #4	$229.86	11.774%	$256.9237	$256.92	$256.90	$256.90
Purchase #5	$191.58	11.161%	$212.9622	$212.96	$212.95	$213.00
Purchase #6	$36.56	10.252%	$40.3081	$40.31	$40.30	$40.30
Purchase #7	$93.38	6.500%	$99.4497	$99.45	$99.45	$99.40
7 purchase totals =	$856.47		$940.2936	$940.29	$940.25	$940.20