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	$53.94	5.270%	$56.7826	$56.78	$56.80	$56.80
Purchase #2	$7.26	3.249%	$7.4959	$7.50	$7.50	$7.50
Purchase #3	$200.65	7.686%	$216.072	$216.07	$216.05	$216.10
Purchase #4	$129.88	9.392%	$142.0783	$142.08	$142.10	$142.10
Purchase #5	$89.90	13.791%	$102.2981	$102.30	$102.30	$102.30
Purchase #6	$183.94	11.577%	$205.2347	$205.23	$205.25	$205.20
Purchase #7	$37.74	12.359%	$42.4043	$42.40	$42.40	$42.40
7 purchase totals =	$703.31		$772.3659	$772.36	$772.40	$772.40