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	$187.89	13.497%	$213.2495	$213.25	$213.25	$213.20
Purchase #2	$54.47	8.643%	$59.1778	$59.18	$59.20	$59.20
Purchase #3	$165.85	13.517%	$188.2679	$188.27	$188.25	$188.30
Purchase #4	$205.55	3.505%	$212.7545	$212.75	$212.75	$212.80
Purchase #5	$145.52	13.361%	$164.9629	$164.96	$164.95	$165.00
Purchase #6	$150.71	10.343%	$166.2979	$166.30	$166.30	$166.30
Purchase #7	$250.77	11.517%	$279.6512	$279.65	$279.65	$279.70
7 purchase totals =	$1,160.76		$1,284.3617	$1,284.36	$1,284.35	$1,284.50