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	$159.42	6.486%	$169.76	$169.76	$169.75	$169.80
Purchase #2	$216.45	8.170%	$234.134	$234.13	$234.15	$234.10
Purchase #3	$81.34	8.593%	$88.3295	$88.33	$88.35	$88.30
Purchase #4	$239.59	13.408%	$271.7142	$271.71	$271.70	$271.70
Purchase #5	$79.94	12.359%	$89.8198	$89.82	$89.80	$89.80
Purchase #6	$231.66	5.540%	$244.494	$244.49	$244.50	$244.50
Purchase #7	$70.59	4.678%	$73.8922	$73.89	$73.90	$73.90
7 purchase totals =	$1,078.99		$1,172.1437	$1,172.13	$1,172.15	$1,172.10