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	$106.55	4.563%	$111.4119	$111.41	$111.40	$111.40
Purchase #2	$175.92	3.832%	$182.6613	$182.66	$182.65	$182.70
Purchase #3	$182.48	7.459%	$196.0912	$196.09	$196.10	$196.10
Purchase #4	$32.53	8.267%	$35.2193	$35.22	$35.20	$35.20
Purchase #5	$209.26	5.443%	$220.65	$220.65	$220.65	$220.70
Purchase #6	$9.29	11.274%	$10.3374	$10.34	$10.35	$10.30
Purchase #7	$167.97	13.445%	$190.5536	$190.55	$190.55	$190.60
7 purchase totals =	$884.00		$946.9247	$946.92	$946.90	$947.00