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	$158.60	5.534%	$167.3769	$167.38	$167.40	$167.40
Purchase #2	$39.31	10.270%	$43.3471	$43.35	$43.35	$43.30
Purchase #3	$29.52	8.391%	$31.997	$32.00	$32.00	$32.00
Purchase #4	$228.35	4.563%	$238.7696	$238.77	$238.75	$238.80
Purchase #5	$180.26	5.646%	$190.4375	$190.44	$190.45	$190.40
Purchase #6	$117.31	11.709%	$131.0458	$131.05	$131.05	$131.00
Purchase #7	$141.33	5.400%	$148.9618	$148.96	$148.95	$149.00
7 purchase totals =	$894.68		$951.9357	$951.95	$951.95	$951.90