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	$217.96	4.840%	$228.5093	$228.51	$228.50	$228.50
Purchase #2	$237.79	11.593%	$265.357	$265.36	$265.35	$265.40
Purchase #3	$12.89	7.685%	$13.8806	$13.88	$13.90	$13.90
Purchase #4	$227.77	7.351%	$244.5134	$244.51	$244.50	$244.50
Purchase #5	$45.41	5.394%	$47.8594	$47.86	$47.85	$47.90
Purchase #6	$178.28	10.456%	$196.921	$196.92	$196.90	$196.90
Purchase #7	$31.49	11.708%	$35.1768	$35.18	$35.20	$35.20
7 purchase totals =	$951.59		$1,032.2175	$1,032.22	$1,032.20	$1,032.30