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	$59.54	10.617%	$65.8614	$65.86	$65.85	$65.90
Purchase #2	$112.75	10.609%	$124.7116	$124.71	$124.70	$124.70
Purchase #3	$208.56	3.834%	$216.5562	$216.56	$216.55	$216.60
Purchase #4	$146.26	9.299%	$159.8607	$159.86	$159.85	$159.90
Purchase #5	$192.43	8.264%	$208.3324	$208.33	$208.35	$208.30
Purchase #6	$84.69	5.287%	$89.1676	$89.17	$89.15	$89.20
Purchase #7	$135.70	11.266%	$150.988	$150.99	$151.00	$151.00
7 purchase totals =	$939.93		$1,015.4779	$1,015.48	$1,015.45	$1,015.60