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	$169.56	9.616%	$185.8649	$185.86	$185.85	$185.90
Purchase #2	$66.29	4.238%	$69.0994	$69.10	$69.10	$69.10
Purchase #3	$238.80	7.360%	$256.3757	$256.38	$256.40	$256.40
Purchase #4	$203.93	7.200%	$218.613	$218.61	$218.60	$218.60
Purchase #5	$202.46	9.629%	$221.9549	$221.95	$221.95	$222.00
Purchase #6	$12.40	8.871%	$13.5	$13.50	$13.50	$13.50
Purchase #7	$104.44	13.414%	$118.4496	$118.45	$118.45	$118.40
7 purchase totals =	$997.88		$1,083.8575	$1,083.85	$1,083.85	$1,083.90