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	$52.45	3.516%	$54.2941	$54.29	$54.30	$54.30
Purchase #2	$42.49	13.675%	$48.3005	$48.30	$48.30	$48.30
Purchase #3	$176.34	5.837%	$186.633	$186.63	$186.65	$186.60
Purchase #4	$168.54	7.141%	$180.5754	$180.58	$180.60	$180.60
Purchase #5	$38.60	4.221%	$40.2293	$40.23	$40.25	$40.20
Purchase #6	$233.50	5.137%	$245.4949	$245.49	$245.50	$245.50
Purchase #7	$130.61	7.681%	$140.6422	$140.64	$140.65	$140.60
7 purchase totals =	$842.53		$896.1694	$896.16	$896.25	$896.10