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	$200.57	10.815%	$222.2616	$222.26	$222.25	$222.30
Purchase #2	$108.87	10.323%	$120.1087	$120.11	$120.10	$120.10
Purchase #3	$248.47	5.839%	$262.9782	$262.98	$263.00	$263.00
Purchase #4	$118.60	7.510%	$127.5069	$127.51	$127.50	$127.50
Purchase #5	$47.88	3.241%	$49.4318	$49.43	$49.45	$49.40
Purchase #6	$78.35	5.441%	$82.613	$82.61	$82.60	$82.60
Purchase #7	$194.26	7.813%	$209.4375	$209.44	$209.45	$209.40
7 purchase totals =	$997.00		$1,074.3377	$1,074.34	$1,074.35	$1,074.30