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	$95.71	3.361%	$98.9268	$98.93	$98.95	$98.90
Purchase #2	$124.54	12.237%	$139.78	$139.78	$139.80	$139.80
Purchase #3	$40.41	5.823%	$42.7631	$42.76	$42.75	$42.80
Purchase #4	$40.32	9.431%	$44.1226	$44.12	$44.10	$44.10
Purchase #5	$249.62	13.602%	$283.5733	$283.57	$283.55	$283.60
Purchase #6	$64.31	12.205%	$72.159	$72.16	$72.15	$72.20
Purchase #7	$97.52	6.696%	$104.0499	$104.05	$104.05	$104.00
7 purchase totals =	$712.43		$785.3747	$785.37	$785.35	$785.40