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	$202.51	6.588%	$215.8514	$215.85	$215.85	$215.90
Purchase #2	$178.61	6.799%	$190.7537	$190.75	$190.75	$190.80
Purchase #3	$148.64	7.490%	$159.7731	$159.77	$159.75	$159.80
Purchase #4	$157.28	13.354%	$178.2832	$178.28	$178.30	$178.30
Purchase #5	$20.29	6.418%	$21.5922	$21.59	$21.60	$21.60
Purchase #6	$12.89	7.501%	$13.8569	$13.86	$13.85	$13.90
Purchase #7	$235.71	12.734%	$265.7253	$265.73	$265.75	$265.70
7 purchase totals =	$955.93		$1,045.8358	$1,045.83	$1,045.85	$1,046.00