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	$137.61	4.446%	$143.7281	$143.73	$143.75	$143.70
Purchase #2	$161.56	9.735%	$177.2879	$177.29	$177.30	$177.30
Purchase #3	$31.82	11.518%	$35.485	$35.49	$35.50	$35.50
Purchase #4	$38.33	10.513%	$42.3596	$42.36	$42.35	$42.40
Purchase #5	$225.76	3.561%	$233.7993	$233.80	$233.80	$233.80
Purchase #6	$204.86	8.605%	$222.4882	$222.49	$222.50	$222.50
Purchase #7	$129.83	12.252%	$145.7368	$145.74	$145.75	$145.70
7 purchase totals =	$929.77		$1,000.8849	$1,000.90	$1,000.95	$1,000.90