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	$31.33	8.558%	$34.0112	$34.01	$34.00	$34.00
Purchase #2	$88.36	13.498%	$100.2868	$100.29	$100.30	$100.30
Purchase #3	$42.25	8.220%	$45.723	$45.72	$45.70	$45.70
Purchase #4	$107.41	12.208%	$120.5226	$120.52	$120.50	$120.50
Purchase #5	$199.78	9.276%	$218.3116	$218.31	$218.30	$218.30
Purchase #6	$17.82	9.663%	$19.5419	$19.54	$19.55	$19.50
Purchase #7	$103.77	7.770%	$111.8329	$111.83	$111.85	$111.80
7 purchase totals =	$590.72		$650.2300	$650.22	$650.20	$650.10