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	$140.91	8.342%	$152.6647	$152.66	$152.65	$152.70
Purchase #2	$156.38	5.611%	$165.1545	$165.15	$165.15	$165.20
Purchase #3	$203.83	12.787%	$229.8937	$229.89	$229.90	$229.90
Purchase #4	$170.29	9.138%	$185.8511	$185.85	$185.85	$185.90
Purchase #5	$139.85	8.458%	$151.6785	$151.68	$151.70	$151.70
Purchase #6	$131.63	6.138%	$139.7094	$139.71	$139.70	$139.70
Purchase #7	$104.53	8.313%	$113.2196	$113.22	$113.20	$113.20
7 purchase totals =	$1,047.42		$1,138.1715	$1,138.16	$1,138.15	$1,138.30