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	$84.26	12.320%	$94.6408	$94.64	$94.65	$94.60
Purchase #2	$134.69	13.260%	$152.5499	$152.55	$152.55	$152.50
Purchase #3	$6.47	12.336%	$7.2681	$7.27	$7.25	$7.30
Purchase #4	$246.53	9.674%	$270.3793	$270.38	$270.40	$270.40
Purchase #5	$44.83	12.778%	$50.5584	$50.56	$50.55	$50.60
Purchase #6	$38.81	10.494%	$42.8827	$42.88	$42.90	$42.90
Purchase #7	$179.94	10.119%	$198.1481	$198.15	$198.15	$198.10
7 purchase totals =	$735.53		$816.4273	$816.43	$816.45	$816.40