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	$83.38	8.411%	$90.3931	$90.39	$90.40	$90.40
Purchase #2	$107.40	4.748%	$112.4994	$112.50	$112.50	$112.50
Purchase #3	$22.32	8.113%	$24.1308	$24.13	$24.15	$24.10
Purchase #4	$99.56	5.250%	$104.7869	$104.79	$104.80	$104.80
Purchase #5	$169.29	3.256%	$174.8021	$174.80	$174.80	$174.80
Purchase #6	$90.77	12.340%	$101.971	$101.97	$101.95	$102.00
Purchase #7	$93.80	5.821%	$99.2601	$99.26	$99.25	$99.30
7 purchase totals =	$666.52		$707.8434	$707.84	$707.85	$707.90