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	$146.67	7.645%	$157.8829	$157.88	$157.90	$157.90
Purchase #2	$139.39	12.370%	$156.6325	$156.63	$156.65	$156.60
Purchase #3	$244.77	10.659%	$270.86	$270.86	$270.85	$270.90
Purchase #4	$74.47	4.748%	$78.0058	$78.01	$78.00	$78.00
Purchase #5	$127.26	11.185%	$141.494	$141.49	$141.50	$141.50
Purchase #6	$75.33	5.594%	$79.544	$79.54	$79.55	$79.50
Purchase #7	$171.25	7.667%	$184.3797	$184.38	$184.40	$184.40
7 purchase totals =	$979.14		$1,068.7989	$1,068.79	$1,068.85	$1,068.80