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	$225.47	3.709%	$233.8327	$233.83	$233.85	$233.80
Purchase #2	$174.43	12.847%	$196.839	$196.84	$196.85	$196.80
Purchase #3	$66.92	5.805%	$70.8047	$70.80	$70.80	$70.80
Purchase #4	$76.52	11.785%	$85.5379	$85.54	$85.55	$85.50
Purchase #5	$142.68	11.417%	$158.9698	$158.97	$158.95	$159.00
Purchase #6	$7.48	3.775%	$7.7624	$7.76	$7.75	$7.80
Purchase #7	$245.46	3.347%	$253.6755	$253.68	$253.70	$253.70
7 purchase totals =	$938.96		$1,007.4220	$1,007.42	$1,007.45	$1,007.40