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	$187.82	12.637%	$211.5548	$211.55	$211.55	$211.60
Purchase #2	$31.33	12.533%	$35.2566	$35.26	$35.25	$35.30
Purchase #3	$13.70	5.533%	$14.458	$14.46	$14.45	$14.50
Purchase #4	$150.71	10.857%	$167.0726	$167.07	$167.05	$167.10
Purchase #5	$33.55	11.460%	$37.3948	$37.39	$37.40	$37.40
Purchase #6	$190.90	7.521%	$205.2576	$205.26	$205.25	$205.30
Purchase #7	$123.86	10.473%	$136.8319	$136.83	$136.85	$136.80
7 purchase totals =	$731.87		$807.8263	$807.82	$807.80	$808.00