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	$64.30	10.423%	$71.002	$71.00	$71.00	$71.00
Purchase #2	$69.78	8.296%	$75.5689	$75.57	$75.55	$75.60
Purchase #3	$16.54	13.742%	$18.8129	$18.81	$18.80	$18.80
Purchase #4	$82.74	13.736%	$94.1052	$94.11	$94.10	$94.10
Purchase #5	$31.63	3.763%	$32.8202	$32.82	$32.80	$32.80
Purchase #6	$246.67	11.328%	$274.6128	$274.61	$274.60	$274.60
Purchase #7	$10.69	10.864%	$11.8514	$11.85	$11.85	$11.90
7 purchase totals =	$522.35		$578.7734	$578.77	$578.70	$578.80