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	$136.65	7.427%	$146.799	$146.80	$146.80	$146.80
Purchase #2	$155.55	9.216%	$169.8855	$169.89	$169.90	$169.90
Purchase #3	$94.37	11.677%	$105.3896	$105.39	$105.40	$105.40
Purchase #4	$242.88	11.397%	$270.561	$270.56	$270.55	$270.60
Purchase #5	$146.47	7.795%	$157.8873	$157.89	$157.90	$157.90
Purchase #6	$138.31	5.602%	$146.0581	$146.06	$146.05	$146.10
Purchase #7	$54.62	8.107%	$59.048	$59.05	$59.05	$59.00
7 purchase totals =	$968.85		$1,055.6285	$1,055.64	$1,055.65	$1,055.70