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	$70.38	10.442%	$77.7291	$77.73	$77.75	$77.70
Purchase #2	$177.63	3.628%	$184.0744	$184.07	$184.05	$184.10
Purchase #3	$137.67	10.668%	$152.3566	$152.36	$152.35	$152.40
Purchase #4	$24.32	13.382%	$27.5745	$27.57	$27.55	$27.60
Purchase #5	$82.96	3.712%	$86.0395	$86.04	$86.05	$86.00
Purchase #6	$180.27	13.464%	$204.5416	$204.54	$204.55	$204.50
Purchase #7	$244.29	4.485%	$255.2464	$255.25	$255.25	$255.20
7 purchase totals =	$917.52		$987.5621	$987.56	$987.55	$987.50