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	$20.69	5.434%	$21.8143	$21.81	$21.80	$21.80
Purchase #2	$59.89	11.631%	$66.8558	$66.86	$66.85	$66.90
Purchase #3	$189.47	12.233%	$212.6479	$212.65	$212.65	$212.60
Purchase #4	$149.63	3.118%	$154.2955	$154.30	$154.30	$154.30
Purchase #5	$211.58	9.507%	$231.6949	$231.69	$231.70	$231.70
Purchase #6	$96.54	9.383%	$105.5983	$105.60	$105.60	$105.60
Purchase #7	$152.65	6.112%	$161.98	$161.98	$162.00	$162.00
7 purchase totals =	$880.45		$954.8867	$954.89	$954.90	$954.90