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	$167.86	13.219%	$190.0494	$190.05	$190.05	$190.00
Purchase #2	$221.75	4.287%	$231.2564	$231.26	$231.25	$231.30
Purchase #3	$188.54	4.407%	$196.849	$196.85	$196.85	$196.80
Purchase #4	$128.38	9.737%	$140.8804	$140.88	$140.90	$140.90
Purchase #5	$145.74	4.250%	$151.934	$151.93	$151.95	$151.90
Purchase #6	$54.89	8.297%	$59.4442	$59.44	$59.45	$59.40
Purchase #7	$221.37	11.539%	$246.9139	$246.91	$246.90	$246.90
7 purchase totals =	$1,128.53		$1,217.3273	$1,217.32	$1,217.35	$1,217.20