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	$191.26	10.264%	$210.8909	$210.89	$210.90	$210.90
Purchase #2	$76.26	8.699%	$82.8939	$82.89	$82.90	$82.90
Purchase #3	$80.96	4.322%	$84.4591	$84.46	$84.45	$84.50
Purchase #4	$77.56	3.780%	$80.4918	$80.49	$80.50	$80.50
Purchase #5	$14.35	6.628%	$15.3011	$15.30	$15.30	$15.30
Purchase #6	$208.55	3.709%	$216.2851	$216.29	$216.30	$216.30
Purchase #7	$89.96	12.142%	$100.8829	$100.88	$100.90	$100.90
7 purchase totals =	$738.90		$791.2048	$791.20	$791.25	$791.30