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	$168.49	11.854%	$188.4628	$188.46	$188.45	$188.50
Purchase #2	$29.29	6.468%	$31.1845	$31.18	$31.20	$31.20
Purchase #3	$188.97	13.730%	$214.9156	$214.92	$214.90	$214.90
Purchase #4	$39.40	6.225%	$41.8527	$41.85	$41.85	$41.90
Purchase #5	$127.33	10.566%	$140.7837	$140.78	$140.80	$140.80
Purchase #6	$63.68	12.300%	$71.5126	$71.51	$71.50	$71.50
Purchase #7	$227.43	11.530%	$253.6527	$253.65	$253.65	$253.70
7 purchase totals =	$844.59		$942.3646	$942.35	$942.35	$942.50