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	$86.56	9.685%	$94.9433	$94.94	$94.95	$94.90
Purchase #2	$69.86	12.135%	$78.3375	$78.34	$78.35	$78.30
Purchase #3	$30.90	11.652%	$34.5005	$34.50	$34.50	$34.50
Purchase #4	$37.73	6.764%	$40.2821	$40.28	$40.30	$40.30
Purchase #5	$230.80	7.406%	$247.893	$247.89	$247.90	$247.90
Purchase #6	$237.98	9.323%	$260.1669	$260.17	$260.15	$260.20
Purchase #7	$47.40	12.498%	$53.3241	$53.32	$53.30	$53.30
7 purchase totals =	$741.23		$809.4474	$809.44	$809.45	$809.40