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	$42.64	3.809%	$44.2642	$44.26	$44.25	$44.30
Purchase #2	$229.71	10.780%	$254.4727	$254.47	$254.45	$254.50
Purchase #3	$237.52	12.415%	$267.0081	$267.01	$267.00	$267.00
Purchase #4	$181.45	8.229%	$196.3815	$196.38	$196.40	$196.40
Purchase #5	$224.89	13.184%	$254.5395	$254.54	$254.55	$254.50
Purchase #6	$68.45	6.178%	$72.6788	$72.68	$72.70	$72.70
Purchase #7	$27.50	13.368%	$31.1762	$31.18	$31.20	$31.20
7 purchase totals =	$1,012.16		$1,120.5210	$1,120.52	$1,120.55	$1,120.60