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	$141.91	10.516%	$156.8333	$156.83	$156.85	$156.80
Purchase #2	$204.50	5.326%	$215.3917	$215.39	$215.40	$215.40
Purchase #3	$222.79	13.676%	$253.2588	$253.26	$253.25	$253.30
Purchase #4	$224.66	7.750%	$242.0712	$242.07	$242.05	$242.10
Purchase #5	$56.51	4.542%	$59.0767	$59.08	$59.10	$59.10
Purchase #6	$130.56	11.397%	$145.4399	$145.44	$145.45	$145.40
Purchase #7	$156.87	5.407%	$165.352	$165.35	$165.35	$165.40
7 purchase totals =	$1,137.80		$1,237.4236	$1,237.42	$1,237.45	$1,237.50