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	$47.26	13.855%	$53.8079	$53.81	$53.80	$53.80
Purchase #2	$213.85	9.545%	$234.262	$234.26	$234.25	$234.30
Purchase #3	$250.84	7.410%	$269.4272	$269.43	$269.45	$269.40
Purchase #4	$118.42	10.409%	$130.7463	$130.75	$130.75	$130.70
Purchase #5	$140.60	11.623%	$156.9419	$156.94	$156.95	$156.90
Purchase #6	$141.44	7.306%	$151.7736	$151.77	$151.75	$151.80
Purchase #7	$40.97	3.626%	$42.4556	$42.46	$42.45	$42.50
7 purchase totals =	$953.38		$1,039.4145	$1,039.42	$1,039.40	$1,039.40