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	$140.26	6.186%	$148.9365	$148.94	$148.95	$148.90
Purchase #2	$69.33	5.445%	$73.105	$73.11	$73.10	$73.10
Purchase #3	$173.78	6.218%	$184.5856	$184.59	$184.60	$184.60
Purchase #4	$95.31	11.148%	$105.9352	$105.94	$105.95	$105.90
Purchase #5	$166.92	4.853%	$175.0206	$175.02	$175.00	$175.00
Purchase #6	$83.96	7.749%	$90.4661	$90.47	$90.45	$90.50
Purchase #7	$247.53	6.738%	$264.2086	$264.21	$264.20	$264.20
7 purchase totals =	$977.09		$1,042.2576	$1,042.28	$1,042.25	$1,042.20