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	$34.25	9.160%	$37.3873	$37.39	$37.40	$37.40
Purchase #2	$73.69	9.329%	$80.5645	$80.56	$80.55	$80.60
Purchase #3	$161.70	13.822%	$184.0502	$184.05	$184.05	$184.10
Purchase #4	$231.99	12.282%	$260.483	$260.48	$260.50	$260.50
Purchase #5	$213.32	8.440%	$231.3242	$231.32	$231.30	$231.30
Purchase #6	$67.55	3.463%	$69.8893	$69.89	$69.90	$69.90
Purchase #7	$233.64	5.852%	$247.3126	$247.31	$247.30	$247.30
7 purchase totals =	$1,016.14		$1,111.0111	$1,111.00	$1,111.00	$1,111.10