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	$178.84	3.706%	$185.4678	$185.47	$185.45	$185.50
Purchase #2	$240.74	9.544%	$263.7162	$263.72	$263.70	$263.70
Purchase #3	$235.29	12.128%	$263.826	$263.83	$263.85	$263.80
Purchase #4	$37.99	11.348%	$42.3011	$42.30	$42.30	$42.30
Purchase #5	$191.52	8.874%	$208.5155	$208.52	$208.50	$208.50
Purchase #6	$58.56	11.569%	$65.3348	$65.33	$65.35	$65.30
Purchase #7	$167.25	7.316%	$179.486	$179.49	$179.50	$179.50
7 purchase totals =	$1,110.19		$1,208.6474	$1,208.66	$1,208.65	$1,208.60