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	$188.89	4.299%	$197.0104	$197.01	$197.00	$197.00
Purchase #2	$95.25	5.125%	$100.1316	$100.13	$100.15	$100.10
Purchase #3	$160.65	11.133%	$178.5352	$178.54	$178.55	$178.50
Purchase #4	$43.96	12.200%	$49.3231	$49.32	$49.30	$49.30
Purchase #5	$78.57	10.713%	$86.9872	$86.99	$87.00	$87.00
Purchase #6	$132.85	13.301%	$150.5204	$150.52	$150.50	$150.50
Purchase #7	$200.28	9.539%	$219.3847	$219.38	$219.40	$219.40
7 purchase totals =	$900.45		$981.8926	$981.89	$981.90	$981.80