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	$219.58	6.164%	$233.1149	$233.11	$233.10	$233.10
Purchase #2	$31.44	10.532%	$34.7513	$34.75	$34.75	$34.80
Purchase #3	$119.68	3.851%	$124.2889	$124.29	$124.30	$124.30
Purchase #4	$80.45	11.491%	$89.6945	$89.69	$89.70	$89.70
Purchase #5	$171.35	13.361%	$194.2441	$194.24	$194.25	$194.20
Purchase #6	$105.29	3.665%	$109.1489	$109.15	$109.15	$109.10
Purchase #7	$148.41	11.827%	$165.9625	$165.96	$165.95	$166.00
7 purchase totals =	$876.20		$951.2051	$951.19	$951.20	$951.20