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	$206.33	6.273%	$219.2731	$219.27	$219.25	$219.30
Purchase #2	$102.34	4.460%	$106.9044	$106.90	$106.90	$106.90
Purchase #3	$57.54	6.503%	$61.2818	$61.28	$61.30	$61.30
Purchase #4	$127.93	12.245%	$143.595	$143.60	$143.60	$143.60
Purchase #5	$81.30	6.119%	$86.2747	$86.27	$86.25	$86.30
Purchase #6	$132.67	10.154%	$146.1413	$146.14	$146.15	$146.10
Purchase #7	$179.62	4.524%	$187.746	$187.75	$187.75	$187.70
7 purchase totals =	$887.73		$951.2163	$951.21	$951.20	$951.20