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	$126.69	11.202%	$140.8818	$140.88	$140.90	$140.90
Purchase #2	$238.93	4.266%	$249.1228	$249.12	$249.10	$249.10
Purchase #3	$213.54	6.117%	$226.6022	$226.60	$226.60	$226.60
Purchase #4	$204.73	12.131%	$229.5658	$229.57	$229.55	$229.60
Purchase #5	$66.34	8.714%	$72.1209	$72.12	$72.10	$72.10
Purchase #6	$72.74	8.465%	$78.8974	$78.90	$78.90	$78.90
Purchase #7	$111.29	8.865%	$121.1559	$121.16	$121.15	$121.20
7 purchase totals =	$1,034.26		$1,118.3468	$1,118.35	$1,118.30	$1,118.40