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	$42.72	13.612%	$48.535	$48.54	$48.55	$48.50
Purchase #2	$96.62	10.494%	$106.7593	$106.76	$106.75	$106.80
Purchase #3	$80.47	3.484%	$83.2736	$83.27	$83.25	$83.30
Purchase #4	$178.59	11.664%	$199.4207	$199.42	$199.40	$199.40
Purchase #5	$138.89	8.223%	$150.3109	$150.31	$150.30	$150.30
Purchase #6	$140.91	12.704%	$158.8112	$158.81	$158.80	$158.80
Purchase #7	$174.34	6.723%	$186.0609	$186.06	$186.05	$186.10
7 purchase totals =	$852.54		$933.1716	$933.17	$933.10	$933.20