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	$205.40	8.521%	$222.9021	$222.90	$222.90	$222.90
Purchase #2	$131.77	7.503%	$141.6567	$141.66	$141.65	$141.70
Purchase #3	$146.54	13.540%	$166.3815	$166.38	$166.40	$166.40
Purchase #4	$229.26	6.396%	$243.9235	$243.92	$243.90	$243.90
Purchase #5	$175.70	5.712%	$185.736	$185.74	$185.75	$185.70
Purchase #6	$35.94	11.149%	$39.947	$39.95	$39.95	$39.90
Purchase #7	$50.95	6.266%	$54.1425	$54.14	$54.15	$54.10
7 purchase totals =	$975.56		$1,054.6893	$1,054.69	$1,054.70	$1,054.60