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	$244.56	9.312%	$267.3334	$267.33	$267.35	$267.30
Purchase #2	$154.28	9.441%	$168.8456	$168.85	$168.85	$168.80
Purchase #3	$9.57	10.820%	$10.6055	$10.61	$10.60	$10.60
Purchase #4	$161.39	13.227%	$182.7371	$182.74	$182.75	$182.70
Purchase #5	$81.97	10.537%	$90.6072	$90.61	$90.60	$90.60
Purchase #6	$242.79	4.664%	$254.1137	$254.11	$254.10	$254.10
Purchase #7	$138.74	7.325%	$148.9027	$148.90	$148.90	$148.90
7 purchase totals =	$1,033.30		$1,123.1452	$1,123.15	$1,123.15	$1,123.00