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	$86.95	13.757%	$98.9117	$98.91	$98.90	$98.90
Purchase #2	$171.88	8.473%	$186.4434	$186.44	$186.45	$186.40
Purchase #3	$33.33	13.514%	$37.8342	$37.83	$37.85	$37.80
Purchase #4	$208.38	9.667%	$228.5241	$228.52	$228.50	$228.50
Purchase #5	$178.40	4.437%	$186.3156	$186.32	$186.30	$186.30
Purchase #6	$85.38	13.629%	$97.0164	$97.02	$97.00	$97.00
Purchase #7	$93.90	5.752%	$99.3011	$99.30	$99.30	$99.30
7 purchase totals =	$858.22		$934.3465	$934.34	$934.30	$934.20