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	$108.47	4.614%	$113.4748	$113.47	$113.45	$113.50
Purchase #2	$59.76	12.726%	$67.3651	$67.37	$67.35	$67.40
Purchase #3	$200.75	13.607%	$228.0661	$228.07	$228.05	$228.10
Purchase #4	$45.77	4.761%	$47.9491	$47.95	$47.95	$47.90
Purchase #5	$182.86	12.110%	$205.0043	$205.00	$205.00	$205.00
Purchase #6	$205.25	3.288%	$211.9986	$212.00	$212.00	$212.00
Purchase #7	$151.56	11.170%	$168.4893	$168.49	$168.50	$168.50
7 purchase totals =	$954.42		$1,042.3473	$1,042.35	$1,042.30	$1,042.40