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	$100.39	13.225%	$113.6666	$113.67	$113.65	$113.70
Purchase #2	$68.88	4.681%	$72.1043	$72.10	$72.10	$72.10
Purchase #3	$99.30	8.635%	$107.8746	$107.87	$107.85	$107.90
Purchase #4	$59.49	12.743%	$67.0708	$67.07	$67.05	$67.10
Purchase #5	$156.76	5.640%	$165.6013	$165.60	$165.60	$165.60
Purchase #6	$111.74	10.760%	$123.7632	$123.76	$123.75	$123.80
Purchase #7	$93.31	12.377%	$104.859	$104.86	$104.85	$104.90
7 purchase totals =	$689.87		$754.9398	$754.93	$754.85	$755.10