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	$225.94	8.827%	$245.8837	$245.88	$245.90	$245.90
Purchase #2	$55.35	3.643%	$57.3664	$57.37	$57.35	$57.40
Purchase #3	$15.66	13.477%	$17.7705	$17.77	$17.75	$17.80
Purchase #4	$245.30	7.417%	$263.4939	$263.49	$263.50	$263.50
Purchase #5	$162.67	8.736%	$176.8809	$176.88	$176.90	$176.90
Purchase #6	$81.38	10.430%	$89.8679	$89.87	$89.85	$89.90
Purchase #7	$138.93	9.730%	$152.4479	$152.45	$152.45	$152.40
7 purchase totals =	$925.23		$1,003.7112	$1,003.71	$1,003.70	$1,003.80