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	$167.91	7.753%	$180.9281	$180.93	$180.95	$180.90
Purchase #2	$103.91	7.554%	$111.7594	$111.76	$111.75	$111.80
Purchase #3	$23.82	3.199%	$24.582	$24.58	$24.60	$24.60
Purchase #4	$6.32	4.660%	$6.6145	$6.61	$6.60	$6.60
Purchase #5	$84.89	8.826%	$92.3824	$92.38	$92.40	$92.40
Purchase #6	$43.83	10.873%	$48.5956	$48.60	$48.60	$48.60
Purchase #7	$157.56	8.653%	$171.1937	$171.19	$171.20	$171.20
7 purchase totals =	$588.24		$636.0557	$636.05	$636.10	$636.10