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	$146.49	7.531%	$157.5222	$157.52	$157.50	$157.50
Purchase #2	$73.66	12.224%	$82.6642	$82.66	$82.65	$82.70
Purchase #3	$148.38	11.703%	$165.7449	$165.74	$165.75	$165.70
Purchase #4	$215.36	8.498%	$233.6613	$233.66	$233.65	$233.70
Purchase #5	$164.95	13.651%	$187.4673	$187.47	$187.45	$187.50
Purchase #6	$69.66	12.688%	$78.4985	$78.50	$78.50	$78.50
Purchase #7	$208.96	6.300%	$222.1245	$222.12	$222.10	$222.10
7 purchase totals =	$1,027.46		$1,127.6829	$1,127.67	$1,127.60	$1,127.70