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	$38.82	10.270%	$42.8068	$42.81	$42.80	$42.80
Purchase #2	$212.52	6.550%	$226.4401	$226.44	$226.45	$226.40
Purchase #3	$248.46	3.217%	$256.453	$256.45	$256.45	$256.50
Purchase #4	$38.31	10.188%	$42.213	$42.21	$42.20	$42.20
Purchase #5	$119.29	11.782%	$133.3447	$133.34	$133.35	$133.30
Purchase #6	$152.33	9.634%	$167.0055	$167.01	$167.00	$167.00
Purchase #7	$204.35	9.389%	$223.5364	$223.54	$223.55	$223.50
7 purchase totals =	$1,014.08		$1,091.7995	$1,091.80	$1,091.80	$1,091.70