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	$155.30	11.160%	$172.6315	$172.63	$172.65	$172.60
Purchase #2	$38.63	4.398%	$40.3289	$40.33	$40.35	$40.30
Purchase #3	$194.59	6.429%	$207.1002	$207.10	$207.10	$207.10
Purchase #4	$81.47	4.188%	$84.882	$84.88	$84.90	$84.90
Purchase #5	$74.34	10.683%	$82.2817	$82.28	$82.30	$82.30
Purchase #6	$67.33	13.230%	$76.2378	$76.24	$76.25	$76.20
Purchase #7	$33.86	10.225%	$37.3222	$37.32	$37.30	$37.30
7 purchase totals =	$645.52		$700.7843	$700.78	$700.85	$700.70