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	$142.35	7.184%	$152.5764	$152.58	$152.60	$152.60
Purchase #2	$48.71	13.276%	$55.1767	$55.18	$55.20	$55.20
Purchase #3	$134.71	4.315%	$140.5227	$140.52	$140.50	$140.50
Purchase #4	$171.56	5.566%	$181.109	$181.11	$181.10	$181.10
Purchase #5	$128.89	4.613%	$134.8357	$134.84	$134.85	$134.80
Purchase #6	$138.79	11.159%	$154.2776	$154.28	$154.30	$154.30
Purchase #7	$153.84	7.854%	$165.9226	$165.92	$165.90	$165.90
7 purchase totals =	$918.85		$984.4207	$984.43	$984.45	$984.40