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	$78.76	11.657%	$87.9411	$87.94	$87.95	$87.90
Purchase #2	$186.59	4.625%	$195.2198	$195.22	$195.20	$195.20
Purchase #3	$45.94	10.141%	$50.5988	$50.60	$50.60	$50.60
Purchase #4	$68.37	13.811%	$77.8126	$77.81	$77.80	$77.80
Purchase #5	$76.91	9.142%	$83.9411	$83.94	$83.95	$83.90
Purchase #6	$53.82	10.478%	$59.4593	$59.46	$59.45	$59.50
Purchase #7	$103.98	8.106%	$112.4086	$112.41	$112.40	$112.40
7 purchase totals =	$614.37		$667.3813	$667.38	$667.35	$667.30