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	$90.30	6.439%	$96.1144	$96.11	$96.10	$96.10
Purchase #2	$62.81	5.141%	$66.0391	$66.04	$66.05	$66.00
Purchase #3	$215.42	7.543%	$231.6691	$231.67	$231.65	$231.70
Purchase #4	$238.78	10.414%	$263.6465	$263.65	$263.65	$263.60
Purchase #5	$32.56	12.221%	$36.5392	$36.54	$36.55	$36.50
Purchase #6	$19.54	4.762%	$20.4705	$20.47	$20.45	$20.50
Purchase #7	$216.73	11.592%	$241.8533	$241.85	$241.85	$241.90
7 purchase totals =	$876.14		$956.3321	$956.33	$956.30	$956.30