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	$178.91	6.626%	$190.7646	$190.76	$190.75	$190.80
Purchase #2	$197.85	12.566%	$222.7118	$222.71	$222.70	$222.70
Purchase #3	$192.83	6.369%	$205.1113	$205.11	$205.10	$205.10
Purchase #4	$51.43	12.526%	$57.8721	$57.87	$57.85	$57.90
Purchase #5	$157.36	13.161%	$178.0701	$178.07	$178.05	$178.10
Purchase #6	$213.34	13.865%	$242.9196	$242.92	$242.90	$242.90
Purchase #7	$75.42	10.419%	$83.278	$83.28	$83.30	$83.30
7 purchase totals =	$1,067.14		$1,180.7275	$1,180.72	$1,180.65	$1,180.80