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	$191.82	7.483%	$206.1739	$206.17	$206.15	$206.20
Purchase #2	$87.30	6.301%	$92.8008	$92.80	$92.80	$92.80
Purchase #3	$131.89	3.727%	$136.8055	$136.81	$136.80	$136.80
Purchase #4	$94.76	8.164%	$102.4962	$102.50	$102.50	$102.50
Purchase #5	$207.48	3.179%	$214.0758	$214.08	$214.10	$214.10
Purchase #6	$149.43	12.829%	$168.6004	$168.60	$168.60	$168.60
Purchase #7	$123.99	13.336%	$140.5253	$140.53	$140.55	$140.50
7 purchase totals =	$986.67		$1,061.4779	$1,061.49	$1,061.50	$1,061.50