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	$43.91	7.597%	$47.2458	$47.25	$47.25	$47.20
Purchase #2	$71.54	11.636%	$79.8644	$79.86	$79.85	$79.90
Purchase #3	$238.42	8.514%	$258.7191	$258.72	$258.70	$258.70
Purchase #4	$237.98	8.633%	$258.5248	$258.52	$258.50	$258.50
Purchase #5	$35.42	12.528%	$39.8574	$39.86	$39.85	$39.90
Purchase #6	$144.48	7.581%	$155.433	$155.43	$155.45	$155.40
Purchase #7	$34.89	7.654%	$37.5605	$37.56	$37.55	$37.60
7 purchase totals =	$806.64		$877.2050	$877.20	$877.15	$877.20