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	$119.70	10.364%	$132.1057	$132.11	$132.10	$132.10
Purchase #2	$53.96	13.562%	$61.2781	$61.28	$61.30	$61.30
Purchase #3	$93.95	10.557%	$103.8683	$103.87	$103.85	$103.90
Purchase #4	$225.98	5.590%	$238.6123	$238.61	$238.60	$238.60
Purchase #5	$18.78	10.571%	$20.7652	$20.77	$20.75	$20.80
Purchase #6	$75.34	8.777%	$81.9526	$81.95	$81.95	$82.00
Purchase #7	$35.47	8.868%	$38.6155	$38.62	$38.60	$38.60
7 purchase totals =	$623.18		$677.1977	$677.21	$677.15	$677.30