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	$93.63	8.793%	$101.8629	$101.86	$101.85	$101.90
Purchase #2	$116.30	5.574%	$122.7826	$122.78	$122.80	$122.80
Purchase #3	$89.36	11.744%	$99.8544	$99.85	$99.85	$99.90
Purchase #4	$136.96	9.758%	$150.3246	$150.32	$150.30	$150.30
Purchase #5	$43.68	11.618%	$48.7547	$48.75	$48.75	$48.80
Purchase #6	$88.51	13.844%	$100.7633	$100.76	$100.75	$100.80
Purchase #7	$59.79	5.656%	$63.1717	$63.17	$63.15	$63.20
7 purchase totals =	$628.23		$687.5142	$687.49	$687.45	$687.70