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	$147.95	4.253%	$154.2423	$154.24	$154.25	$154.20
Purchase #2	$34.79	9.222%	$37.9983	$38.00	$38.00	$38.00
Purchase #3	$116.76	13.403%	$132.4093	$132.41	$132.40	$132.40
Purchase #4	$84.36	6.711%	$90.0214	$90.02	$90.00	$90.00
Purchase #5	$245.89	7.746%	$264.9366	$264.94	$264.95	$264.90
Purchase #6	$146.87	11.859%	$164.2873	$164.29	$164.30	$164.30
Purchase #7	$136.47	11.139%	$151.6714	$151.67	$151.65	$151.70
7 purchase totals =	$913.09		$995.5666	$995.57	$995.55	$995.50