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	$150.56	9.602%	$165.0168	$165.02	$165.00	$165.00
Purchase #2	$249.89	3.797%	$259.3783	$259.38	$259.40	$259.40
Purchase #3	$63.56	12.476%	$71.4897	$71.49	$71.50	$71.50
Purchase #4	$158.34	4.497%	$165.4605	$165.46	$165.45	$165.50
Purchase #5	$172.59	9.171%	$188.4182	$188.42	$188.40	$188.40
Purchase #6	$71.34	5.624%	$75.3522	$75.35	$75.35	$75.40
Purchase #7	$215.48	9.699%	$236.3794	$236.38	$236.40	$236.40
7 purchase totals =	$1,081.76		$1,161.4951	$1,161.50	$1,161.50	$1,161.60