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	$13.36	5.567%	$14.1038	$14.10	$14.10	$14.10
Purchase #2	$88.55	3.782%	$91.899	$91.90	$91.90	$91.90
Purchase #3	$133.45	13.858%	$151.9435	$151.94	$151.95	$151.90
Purchase #4	$106.92	13.480%	$121.3328	$121.33	$121.35	$121.30
Purchase #5	$59.95	7.864%	$64.6645	$64.66	$64.65	$64.70
Purchase #6	$105.38	13.489%	$119.5947	$119.59	$119.60	$119.60
Purchase #7	$101.29	8.555%	$109.9554	$109.96	$109.95	$110.00
7 purchase totals =	$608.90		$673.4937	$673.48	$673.50	$673.50