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	$168.45	4.742%	$176.4379	$176.44	$176.45	$176.40
Purchase #2	$109.83	4.259%	$114.5077	$114.51	$114.50	$114.50
Purchase #3	$133.63	13.847%	$152.1337	$152.13	$152.15	$152.10
Purchase #4	$135.78	5.349%	$143.0429	$143.04	$143.05	$143.00
Purchase #5	$59.26	3.303%	$61.2174	$61.22	$61.20	$61.20
Purchase #6	$173.58	8.601%	$188.5096	$188.51	$188.50	$188.50
Purchase #7	$12.27	9.684%	$13.4582	$13.46	$13.45	$13.50
7 purchase totals =	$792.80		$849.3074	$849.31	$849.30	$849.20