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	$59.67	6.324%	$63.4435	$63.44	$63.45	$63.40
Purchase #2	$141.79	4.793%	$148.586	$148.59	$148.60	$148.60
Purchase #3	$42.34	3.334%	$43.7516	$43.75	$43.75	$43.80
Purchase #4	$50.34	13.151%	$56.9602	$56.96	$56.95	$57.00
Purchase #5	$218.56	4.512%	$228.4214	$228.42	$228.40	$228.40
Purchase #6	$63.97	11.795%	$71.5153	$71.52	$71.50	$71.50
Purchase #7	$98.53	5.305%	$103.757	$103.76	$103.75	$103.80
7 purchase totals =	$675.20		$716.4350	$716.44	$716.40	$716.50