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	$90.55	8.811%	$98.5284	$98.53	$98.55	$98.50
Purchase #2	$138.41	9.228%	$151.1825	$151.18	$151.20	$151.20
Purchase #3	$237.45	8.190%	$256.8972	$256.90	$256.90	$256.90
Purchase #4	$149.58	11.527%	$166.8221	$166.82	$166.80	$166.80
Purchase #5	$175.34	12.129%	$196.607	$196.61	$196.60	$196.60
Purchase #6	$142.77	8.194%	$154.4686	$154.47	$154.45	$154.50
Purchase #7	$196.85	7.327%	$211.2732	$211.27	$211.25	$211.30
7 purchase totals =	$1,130.95		$1,235.7790	$1,235.78	$1,235.75	$1,235.80