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	$73.98	4.593%	$77.3779	$77.38	$77.40	$77.40
Purchase #2	$126.66	3.111%	$130.6004	$130.60	$130.60	$130.60
Purchase #3	$78.57	5.529%	$82.9141	$82.91	$82.90	$82.90
Purchase #4	$119.90	11.716%	$133.9475	$133.95	$133.95	$133.90
Purchase #5	$78.90	8.248%	$85.4077	$85.41	$85.40	$85.40
Purchase #6	$77.95	3.430%	$80.6237	$80.62	$80.60	$80.60
Purchase #7	$235.86	13.830%	$268.4794	$268.48	$268.50	$268.50
7 purchase totals =	$791.82		$859.3507	$859.35	$859.35	$859.30