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	$34.95	10.227%	$38.5243	$38.52	$38.50	$38.50
Purchase #2	$109.33	12.613%	$123.1198	$123.12	$123.10	$123.10
Purchase #3	$10.29	11.606%	$11.4843	$11.48	$11.50	$11.50
Purchase #4	$7.25	9.592%	$7.9454	$7.95	$7.95	$7.90
Purchase #5	$243.99	12.614%	$274.7669	$274.77	$274.75	$274.80
Purchase #6	$152.34	13.191%	$172.4352	$172.44	$172.45	$172.40
Purchase #7	$148.54	13.374%	$168.4057	$168.41	$168.40	$168.40
7 purchase totals =	$706.69		$796.6816	$796.69	$796.65	$796.60