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	$54.97	11.815%	$61.4647	$61.46	$61.45	$61.50
Purchase #2	$32.27	4.219%	$33.6315	$33.63	$33.65	$33.60
Purchase #3	$118.79	3.671%	$123.1508	$123.15	$123.15	$123.20
Purchase #4	$144.82	8.264%	$156.7879	$156.79	$156.80	$156.80
Purchase #5	$19.74	7.139%	$21.1492	$21.15	$21.15	$21.10
Purchase #6	$55.76	3.684%	$57.8142	$57.81	$57.80	$57.80
Purchase #7	$52.64	10.298%	$58.0609	$58.06	$58.05	$58.10
7 purchase totals =	$478.99		$512.0592	$512.05	$512.05	$512.10