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	$157.80	6.755%	$168.4594	$168.46	$168.45	$168.50
Purchase #2	$92.50	7.208%	$99.1674	$99.17	$99.15	$99.20
Purchase #3	$70.41	3.850%	$73.1208	$73.12	$73.10	$73.10
Purchase #4	$186.74	3.508%	$193.2908	$193.29	$193.30	$193.30
Purchase #5	$228.81	3.516%	$236.855	$236.86	$236.85	$236.90
Purchase #6	$66.38	9.379%	$72.6058	$72.61	$72.60	$72.60
Purchase #7	$59.96	5.680%	$63.3657	$63.37	$63.35	$63.40
7 purchase totals =	$862.60		$906.8649	$906.88	$906.80	$907.00