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	$57.92	8.102%	$62.6127	$62.61	$62.60	$62.60
Purchase #2	$90.53	7.146%	$96.9993	$97.00	$97.00	$97.00
Purchase #3	$176.94	7.584%	$190.3591	$190.36	$190.35	$190.40
Purchase #4	$137.92	10.772%	$152.7767	$152.78	$152.80	$152.80
Purchase #5	$58.93	3.520%	$61.0043	$61.00	$61.00	$61.00
Purchase #6	$237.60	5.523%	$250.7226	$250.72	$250.70	$250.70
Purchase #7	$166.82	9.284%	$182.3076	$182.31	$182.30	$182.30
7 purchase totals =	$926.66		$996.7823	$996.78	$996.75	$996.80