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	$69.31	12.317%	$77.8469	$77.85	$77.85	$77.80
Purchase #2	$117.82	11.665%	$131.5637	$131.56	$131.55	$131.60
Purchase #3	$60.25	11.660%	$67.2752	$67.28	$67.30	$67.30
Purchase #4	$222.41	3.388%	$229.9453	$229.95	$229.95	$229.90
Purchase #5	$68.43	3.316%	$70.6991	$70.70	$70.70	$70.70
Purchase #6	$90.72	4.737%	$95.0174	$95.02	$95.00	$95.00
Purchase #7	$73.45	9.266%	$80.2559	$80.26	$80.25	$80.30
7 purchase totals =	$702.39		$752.6035	$752.62	$752.60	$752.60