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	$110.85	7.507%	$119.1715	$119.17	$119.15	$119.20
Purchase #2	$195.40	4.815%	$204.8085	$204.81	$204.80	$204.80
Purchase #3	$176.59	11.379%	$196.6842	$196.68	$196.70	$196.70
Purchase #4	$168.27	13.412%	$190.8384	$190.84	$190.85	$190.80
Purchase #5	$86.28	9.854%	$94.782	$94.78	$94.80	$94.80
Purchase #6	$73.88	13.143%	$83.59	$83.59	$83.60	$83.60
Purchase #7	$13.78	9.405%	$15.076	$15.08	$15.10	$15.10
7 purchase totals =	$825.05		$904.9506	$904.95	$905.00	$905.00