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	$87.50	5.242%	$92.0868	$92.09	$92.10	$92.10
Purchase #2	$180.88	13.473%	$205.25	$205.25	$205.25	$205.30
Purchase #3	$122.66	4.165%	$127.7688	$127.77	$127.75	$127.80
Purchase #4	$38.53	5.268%	$40.5598	$40.56	$40.55	$40.60
Purchase #5	$242.93	5.578%	$256.4806	$256.48	$256.50	$256.50
Purchase #6	$59.53	10.228%	$65.6187	$65.62	$65.60	$65.60
Purchase #7	$84.46	6.291%	$89.7734	$89.77	$89.75	$89.80
7 purchase totals =	$816.49		$877.5381	$877.54	$877.50	$877.70