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	$62.32	8.117%	$67.3785	$67.38	$67.40	$67.40
Purchase #2	$245.65	5.161%	$258.328	$258.33	$258.35	$258.30
Purchase #3	$202.43	10.280%	$223.2398	$223.24	$223.25	$223.20
Purchase #4	$11.63	10.295%	$12.8273	$12.83	$12.85	$12.80
Purchase #5	$243.82	8.381%	$264.2546	$264.25	$264.25	$264.30
Purchase #6	$33.38	11.504%	$37.22	$37.22	$37.20	$37.20
Purchase #7	$103.64	10.288%	$114.3025	$114.30	$114.30	$114.30
7 purchase totals =	$902.87		$977.5507	$977.55	$977.60	$977.50