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	$152.55	11.814%	$170.5723	$170.57	$170.55	$170.60
Purchase #2	$137.41	11.269%	$152.8947	$152.89	$152.90	$152.90
Purchase #3	$124.40	6.127%	$132.022	$132.02	$132.00	$132.00
Purchase #4	$189.36	13.341%	$214.6225	$214.62	$214.60	$214.60
Purchase #5	$140.82	8.667%	$153.0249	$153.02	$153.00	$153.00
Purchase #6	$250.53	11.593%	$279.5739	$279.57	$279.55	$279.60
Purchase #7	$19.28	5.585%	$20.3568	$20.36	$20.35	$20.40
7 purchase totals =	$1,014.35		$1,123.0671	$1,123.05	$1,122.95	$1,123.10