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	$58.71	4.423%	$61.3067	$61.31	$61.30	$61.30
Purchase #2	$125.51	13.510%	$142.4664	$142.47	$142.45	$142.50
Purchase #3	$166.94	7.250%	$179.0432	$179.04	$179.05	$179.00
Purchase #4	$199.57	6.420%	$212.3824	$212.38	$212.40	$212.40
Purchase #5	$204.86	8.393%	$222.0539	$222.05	$222.05	$222.10
Purchase #6	$27.73	12.543%	$31.2082	$31.21	$31.20	$31.20
Purchase #7	$125.82	5.594%	$132.8584	$132.86	$132.85	$132.90
7 purchase totals =	$909.14		$981.3192	$981.32	$981.30	$981.40