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	$126.95	3.671%	$131.6103	$131.61	$131.60	$131.60
Purchase #2	$98.66	11.132%	$109.6428	$109.64	$109.65	$109.60
Purchase #3	$218.69	13.368%	$247.9245	$247.92	$247.90	$247.90
Purchase #4	$187.28	6.608%	$199.6555	$199.66	$199.65	$199.70
Purchase #5	$93.50	13.160%	$105.8046	$105.80	$105.80	$105.80
Purchase #6	$127.25	11.866%	$142.3495	$142.35	$142.35	$142.30
Purchase #7	$35.86	13.782%	$40.8022	$40.80	$40.80	$40.80
7 purchase totals =	$888.19		$977.7894	$977.78	$977.75	$977.70