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	$152.33	8.850%	$165.8112	$165.81	$165.80	$165.80
Purchase #2	$131.27	7.539%	$141.1664	$141.17	$141.15	$141.20
Purchase #3	$72.38	11.427%	$80.6509	$80.65	$80.65	$80.70
Purchase #4	$55.90	6.212%	$59.3725	$59.37	$59.35	$59.40
Purchase #5	$105.93	10.383%	$116.9287	$116.93	$116.95	$116.90
Purchase #6	$35.57	9.162%	$38.8289	$38.83	$38.85	$38.80
Purchase #7	$243.49	6.856%	$260.1837	$260.18	$260.20	$260.20
7 purchase totals =	$796.87		$862.9423	$862.94	$862.95	$863.00