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	$200.37	11.198%	$222.8074	$222.81	$222.80	$222.80
Purchase #2	$92.41	6.589%	$98.4989	$98.50	$98.50	$98.50
Purchase #3	$244.55	5.650%	$258.3671	$258.37	$258.35	$258.40
Purchase #4	$53.85	5.843%	$56.9965	$57.00	$57.00	$57.00
Purchase #5	$147.89	13.544%	$167.9202	$167.92	$167.90	$167.90
Purchase #6	$29.58	6.655%	$31.5485	$31.55	$31.55	$31.50
Purchase #7	$48.59	9.601%	$53.2551	$53.26	$53.25	$53.30
7 purchase totals =	$817.24		$889.3937	$889.41	$889.35	$889.40