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	$244.92	3.418%	$253.2914	$253.29	$253.30	$253.30
Purchase #2	$36.72	11.224%	$40.8415	$40.84	$40.85	$40.80
Purchase #3	$235.37	4.217%	$245.2956	$245.30	$245.30	$245.30
Purchase #4	$55.80	13.804%	$63.5026	$63.50	$63.50	$63.50
Purchase #5	$219.59	8.494%	$238.242	$238.24	$238.25	$238.20
Purchase #6	$36.76	10.161%	$40.4952	$40.50	$40.50	$40.50
Purchase #7	$241.84	12.358%	$271.7266	$271.73	$271.75	$271.70
7 purchase totals =	$1,071.00		$1,153.3949	$1,153.40	$1,153.45	$1,153.30