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	$89.44	9.827%	$98.2293	$98.23	$98.25	$98.20
Purchase #2	$30.80	8.814%	$33.5147	$33.51	$33.50	$33.50
Purchase #3	$94.48	4.322%	$98.5634	$98.56	$98.55	$98.60
Purchase #4	$82.56	13.184%	$93.4447	$93.44	$93.45	$93.40
Purchase #5	$35.89	4.126%	$37.3708	$37.37	$37.35	$37.40
Purchase #6	$196.71	11.371%	$219.0779	$219.08	$219.10	$219.10
Purchase #7	$50.60	3.676%	$52.4601	$52.46	$52.45	$52.50
7 purchase totals =	$580.48		$632.6609	$632.65	$632.65	$632.70