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	$197.46	12.565%	$222.2708	$222.27	$222.25	$222.30
Purchase #2	$49.48	7.357%	$53.1202	$53.12	$53.10	$53.10
Purchase #3	$147.87	7.697%	$159.2516	$159.25	$159.25	$159.30
Purchase #4	$126.82	12.788%	$143.0377	$143.04	$143.05	$143.00
Purchase #5	$118.58	11.646%	$132.3898	$132.39	$132.40	$132.40
Purchase #6	$135.66	10.650%	$150.1078	$150.11	$150.10	$150.10
Purchase #7	$205.77	8.267%	$222.781	$222.78	$222.80	$222.80
7 purchase totals =	$981.64		$1,082.9589	$1,082.96	$1,082.95	$1,083.00