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	$224.86	7.571%	$241.8842	$241.88	$241.90	$241.90
Purchase #2	$185.85	13.475%	$210.8933	$210.89	$210.90	$210.90
Purchase #3	$178.96	3.810%	$185.7784	$185.78	$185.80	$185.80
Purchase #4	$246.32	13.580%	$279.7703	$279.77	$279.75	$279.80
Purchase #5	$156.62	5.386%	$165.0556	$165.06	$165.05	$165.10
Purchase #6	$63.58	7.549%	$68.3797	$68.38	$68.40	$68.40
Purchase #7	$52.25	12.120%	$58.5827	$58.58	$58.60	$58.60
7 purchase totals =	$1,108.44		$1,210.3442	$1,210.34	$1,210.40	$1,210.50