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	$189.81	6.155%	$201.4928	$201.49	$201.50	$201.50
Purchase #2	$91.79	7.375%	$98.5595	$98.56	$98.55	$98.60
Purchase #3	$89.92	11.623%	$100.3714	$100.37	$100.35	$100.40
Purchase #4	$221.63	5.426%	$233.6556	$233.66	$233.65	$233.70
Purchase #5	$119.58	9.343%	$130.7524	$130.75	$130.75	$130.80
Purchase #6	$87.54	9.423%	$95.7889	$95.79	$95.80	$95.80
Purchase #7	$65.77	10.788%	$72.8653	$72.87	$72.85	$72.90
7 purchase totals =	$866.04		$933.4859	$933.49	$933.45	$933.70