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	$41.89	10.872%	$46.4443	$46.44	$46.45	$46.40
Purchase #2	$61.35	3.478%	$63.4838	$63.48	$63.50	$63.50
Purchase #3	$38.91	9.172%	$42.4788	$42.48	$42.50	$42.50
Purchase #4	$131.93	5.792%	$139.5714	$139.57	$139.55	$139.60
Purchase #5	$41.97	11.740%	$46.8973	$46.90	$46.90	$46.90
Purchase #6	$97.67	7.194%	$104.6964	$104.70	$104.70	$104.70
Purchase #7	$11.62	8.632%	$12.623	$12.62	$12.60	$12.60
7 purchase totals =	$425.34		$456.1950	$456.19	$456.20	$456.20