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	$66.91	6.704%	$71.3956	$71.40	$71.40	$71.40
Purchase #2	$140.47	10.703%	$155.5045	$155.50	$155.50	$155.50
Purchase #3	$54.70	8.183%	$59.1761	$59.18	$59.20	$59.20
Purchase #4	$31.96	6.445%	$34.0198	$34.02	$34.00	$34.00
Purchase #5	$217.74	7.209%	$233.4369	$233.44	$233.45	$233.40
Purchase #6	$45.38	6.731%	$48.4345	$48.43	$48.45	$48.40
Purchase #7	$218.31	11.152%	$242.6559	$242.66	$242.65	$242.70
7 purchase totals =	$775.47		$844.6233	$844.63	$844.65	$844.60