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	$118.87	4.110%	$123.7556	$123.76	$123.75	$123.80
Purchase #2	$177.71	13.613%	$201.9017	$201.90	$201.90	$201.90
Purchase #3	$96.86	3.561%	$100.3092	$100.31	$100.30	$100.30
Purchase #4	$165.82	13.704%	$188.544	$188.54	$188.55	$188.50
Purchase #5	$215.70	3.783%	$223.8599	$223.86	$223.85	$223.90
Purchase #6	$250.45	9.765%	$274.9064	$274.91	$274.90	$274.90
Purchase #7	$107.33	10.606%	$118.7134	$118.71	$118.70	$118.70
7 purchase totals =	$1,132.74		$1,231.9902	$1,231.99	$1,231.95	$1,232.00