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	$122.83	3.405%	$127.0124	$127.01	$127.00	$127.00
Purchase #2	$38.57	3.418%	$39.8883	$39.89	$39.90	$39.90
Purchase #3	$221.31	7.268%	$237.3948	$237.39	$237.40	$237.40
Purchase #4	$9.32	10.698%	$10.3171	$10.32	$10.30	$10.30
Purchase #5	$228.47	6.592%	$243.5307	$243.53	$243.55	$243.50
Purchase #6	$35.33	6.564%	$37.6491	$37.65	$37.65	$37.60
Purchase #7	$220.64	13.211%	$249.7888	$249.79	$249.80	$249.80
7 purchase totals =	$876.47		$945.5812	$945.58	$945.60	$945.50