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	$6.52	9.498%	$7.1393	$7.14	$7.15	$7.10
Purchase #2	$137.89	5.673%	$145.7125	$145.71	$145.70	$145.70
Purchase #3	$212.39	3.272%	$219.3394	$219.34	$219.35	$219.30
Purchase #4	$151.60	11.140%	$168.4882	$168.49	$168.50	$168.50
Purchase #5	$197.65	12.158%	$221.6803	$221.68	$221.70	$221.70
Purchase #6	$233.52	12.519%	$262.7544	$262.75	$262.75	$262.80
Purchase #7	$62.95	9.787%	$69.1109	$69.11	$69.10	$69.10
7 purchase totals =	$1,002.52		$1,094.2250	$1,094.22	$1,094.25	$1,094.20