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	$220.89	11.144%	$245.506	$245.51	$245.50	$245.50
Purchase #2	$158.68	12.533%	$178.5674	$178.57	$178.55	$178.60
Purchase #3	$99.68	3.496%	$103.1648	$103.16	$103.15	$103.20
Purchase #4	$205.41	13.722%	$233.5964	$233.60	$233.60	$233.60
Purchase #5	$87.46	12.458%	$98.3558	$98.36	$98.35	$98.40
Purchase #6	$88.56	9.240%	$96.7429	$96.74	$96.75	$96.70
Purchase #7	$169.50	12.556%	$190.7824	$190.78	$190.80	$190.80
7 purchase totals =	$1,030.18		$1,146.7157	$1,146.72	$1,146.70	$1,146.80