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	$55.47	13.786%	$63.1171	$63.12	$63.10	$63.10
Purchase #2	$31.36	4.567%	$32.7922	$32.79	$32.80	$32.80
Purchase #3	$174.37	9.280%	$190.5515	$190.55	$190.55	$190.60
Purchase #4	$95.43	11.387%	$106.2966	$106.30	$106.30	$106.30
Purchase #5	$96.77	3.802%	$100.4492	$100.45	$100.45	$100.40
Purchase #6	$37.87	13.860%	$43.1188	$43.12	$43.10	$43.10
Purchase #7	$106.86	5.449%	$112.6828	$112.68	$112.70	$112.70
7 purchase totals =	$598.13		$649.0082	$649.01	$649.00	$649.00