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	$144.71	13.548%	$164.3153	$164.32	$164.30	$164.30
Purchase #2	$126.65	3.324%	$130.8598	$130.86	$130.85	$130.90
Purchase #3	$171.90	6.377%	$182.8621	$182.86	$182.85	$182.90
Purchase #4	$6.80	7.708%	$7.3241	$7.32	$7.30	$7.30
Purchase #5	$118.26	3.368%	$122.243	$122.24	$122.25	$122.20
Purchase #6	$176.50	13.572%	$200.4546	$200.45	$200.45	$200.50
Purchase #7	$152.42	7.741%	$164.2188	$164.22	$164.20	$164.20
7 purchase totals =	$897.24		$972.2777	$972.27	$972.20	$972.30