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	$101.31	11.626%	$113.0883	$113.09	$113.10	$113.10
Purchase #2	$6.64	6.365%	$7.0626	$7.06	$7.05	$7.10
Purchase #3	$136.42	7.417%	$146.5383	$146.54	$146.55	$146.50
Purchase #4	$250.78	9.108%	$273.621	$273.62	$273.60	$273.60
Purchase #5	$68.98	13.235%	$78.1095	$78.11	$78.10	$78.10
Purchase #6	$187.93	6.689%	$200.5006	$200.50	$200.50	$200.50
Purchase #7	$14.38	3.324%	$14.858	$14.86	$14.85	$14.90
7 purchase totals =	$766.44		$833.7783	$833.78	$833.75	$833.80