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	$63.91	12.530%	$71.9179	$71.92	$71.90	$71.90
Purchase #2	$65.57	3.288%	$67.7259	$67.73	$67.75	$67.70
Purchase #3	$171.51	12.318%	$192.6366	$192.64	$192.65	$192.60
Purchase #4	$236.42	8.602%	$256.7568	$256.76	$256.75	$256.80
Purchase #5	$96.50	7.137%	$103.3872	$103.39	$103.40	$103.40
Purchase #6	$39.30	6.520%	$41.8624	$41.86	$41.85	$41.90
Purchase #7	$123.50	3.439%	$127.7472	$127.75	$127.75	$127.70
7 purchase totals =	$796.71		$862.0340	$862.05	$862.05	$862.00