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	$228.80	4.369%	$238.7963	$238.80	$238.80	$238.80
Purchase #2	$165.94	7.395%	$178.2113	$178.21	$178.20	$178.20
Purchase #3	$10.25	8.219%	$11.0924	$11.09	$11.10	$11.10
Purchase #4	$88.86	5.690%	$93.9161	$93.92	$93.90	$93.90
Purchase #5	$208.89	9.782%	$229.3236	$229.32	$229.30	$229.30
Purchase #6	$33.64	12.782%	$37.9399	$37.94	$37.95	$37.90
Purchase #7	$71.31	9.855%	$78.3376	$78.34	$78.35	$78.30
7 purchase totals =	$807.69		$867.6172	$867.62	$867.60	$867.50