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	$133.26	11.159%	$148.1305	$148.13	$148.15	$148.10
Purchase #2	$127.28	9.828%	$139.7891	$139.79	$139.80	$139.80
Purchase #3	$38.54	5.108%	$40.5086	$40.51	$40.50	$40.50
Purchase #4	$149.82	7.647%	$161.2767	$161.28	$161.30	$161.30
Purchase #5	$248.44	12.645%	$279.8552	$279.86	$279.85	$279.90
Purchase #6	$62.69	8.298%	$67.892	$67.89	$67.90	$67.90
Purchase #7	$132.85	9.407%	$145.3472	$145.35	$145.35	$145.30
7 purchase totals =	$892.88		$982.7993	$982.81	$982.85	$982.80