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	$63.32	5.320%	$66.6886	$66.69	$66.70	$66.70
Purchase #2	$114.60	13.673%	$130.2693	$130.27	$130.25	$130.30
Purchase #3	$111.95	10.282%	$123.4607	$123.46	$123.45	$123.50
Purchase #4	$103.53	12.353%	$116.3191	$116.32	$116.30	$116.30
Purchase #5	$141.86	10.148%	$156.256	$156.26	$156.25	$156.30
Purchase #6	$249.48	11.576%	$278.3598	$278.36	$278.35	$278.40
Purchase #7	$139.78	13.306%	$158.3791	$158.38	$158.40	$158.40
7 purchase totals =	$924.52		$1,029.7326	$1,029.74	$1,029.70	$1,029.90