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	$100.61	4.108%	$104.7431	$104.74	$104.75	$104.70
Purchase #2	$167.46	7.283%	$179.6561	$179.66	$179.65	$179.70
Purchase #3	$126.48	4.193%	$131.7833	$131.78	$131.80	$131.80
Purchase #4	$30.32	4.580%	$31.7087	$31.71	$31.70	$31.70
Purchase #5	$150.25	9.225%	$164.1106	$164.11	$164.10	$164.10
Purchase #6	$125.59	12.512%	$141.3038	$141.30	$141.30	$141.30
Purchase #7	$166.52	7.450%	$178.9257	$178.93	$178.95	$178.90
7 purchase totals =	$867.23		$932.2313	$932.23	$932.25	$932.20