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	$226.88	3.336%	$234.4487	$234.45	$234.45	$234.40
Purchase #2	$29.48	12.825%	$33.2608	$33.26	$33.25	$33.30
Purchase #3	$126.85	4.333%	$132.3464	$132.35	$132.35	$132.30
Purchase #4	$125.61	11.554%	$140.123	$140.12	$140.10	$140.10
Purchase #5	$245.53	12.129%	$275.3103	$275.31	$275.30	$275.30
Purchase #6	$249.51	5.616%	$263.5225	$263.52	$263.50	$263.50
Purchase #7	$35.88	12.292%	$40.2904	$40.29	$40.30	$40.30
7 purchase totals =	$1,039.74		$1,119.3021	$1,119.30	$1,119.25	$1,119.20