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	$78.47	9.452%	$85.887	$85.89	$85.90	$85.90
Purchase #2	$19.46	3.225%	$20.0876	$20.09	$20.10	$20.10
Purchase #3	$86.98	6.696%	$92.8042	$92.80	$92.80	$92.80
Purchase #4	$60.61	13.265%	$68.6499	$68.65	$68.65	$68.60
Purchase #5	$136.81	10.819%	$151.6115	$151.61	$151.60	$151.60
Purchase #6	$141.92	6.429%	$151.044	$151.04	$151.05	$151.00
Purchase #7	$140.72	8.465%	$152.6319	$152.63	$152.65	$152.60
7 purchase totals =	$664.97		$722.7161	$722.71	$722.75	$722.60