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	$210.66	5.510%	$222.2674	$222.27	$222.25	$222.30
Purchase #2	$152.82	12.685%	$172.2052	$172.21	$172.20	$172.20
Purchase #3	$197.56	4.404%	$206.2605	$206.26	$206.25	$206.30
Purchase #4	$56.77	8.253%	$61.4552	$61.46	$61.45	$61.50
Purchase #5	$111.70	6.411%	$118.8611	$118.86	$118.85	$118.90
Purchase #6	$241.50	8.473%	$261.9623	$261.96	$261.95	$262.00
Purchase #7	$82.86	11.583%	$92.4577	$92.46	$92.45	$92.50
7 purchase totals =	$1,053.87		$1,135.4694	$1,135.48	$1,135.40	$1,135.70