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	$149.33	11.534%	$166.5537	$166.55	$166.55	$166.60
Purchase #2	$40.69	3.288%	$42.0279	$42.03	$42.05	$42.00
Purchase #3	$31.84	5.195%	$33.4941	$33.49	$33.50	$33.50
Purchase #4	$30.48	13.734%	$34.6661	$34.67	$34.65	$34.70
Purchase #5	$81.56	13.441%	$92.5225	$92.52	$92.50	$92.50
Purchase #6	$38.55	13.239%	$43.6536	$43.65	$43.65	$43.70
Purchase #7	$87.56	13.317%	$99.2204	$99.22	$99.20	$99.20
7 purchase totals =	$460.01		$512.1383	$512.13	$512.10	$512.20