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	$6.71	3.384%	$6.9371	$6.94	$6.95	$6.90
Purchase #2	$87.43	7.658%	$94.1254	$94.13	$94.15	$94.10
Purchase #3	$242.82	9.571%	$266.0603	$266.06	$266.05	$266.10
Purchase #4	$242.91	5.287%	$255.7527	$255.75	$255.75	$255.80
Purchase #5	$200.50	13.721%	$228.0106	$228.01	$228.00	$228.00
Purchase #6	$173.50	9.734%	$190.3885	$190.39	$190.40	$190.40
Purchase #7	$149.73	10.559%	$165.54	$165.54	$165.55	$165.50
7 purchase totals =	$1,103.60		$1,206.8146	$1,206.82	$1,206.85	$1,206.80