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	$168.77	5.832%	$178.6127	$178.61	$178.60	$178.60
Purchase #2	$102.37	11.843%	$114.4937	$114.49	$114.50	$114.50
Purchase #3	$89.47	11.480%	$99.7412	$99.74	$99.75	$99.70
Purchase #4	$178.73	6.750%	$190.7943	$190.79	$190.80	$190.80
Purchase #5	$182.36	6.201%	$193.6681	$193.67	$193.65	$193.70
Purchase #6	$95.99	8.274%	$103.9322	$103.93	$103.95	$103.90
Purchase #7	$56.28	5.746%	$59.5138	$59.51	$59.50	$59.50
7 purchase totals =	$873.97		$940.7560	$940.74	$940.75	$940.70