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	$102.52	9.525%	$112.285	$112.29	$112.30	$112.30
Purchase #2	$201.69	13.303%	$228.5208	$228.52	$228.50	$228.50
Purchase #3	$55.66	9.854%	$61.1447	$61.14	$61.15	$61.10
Purchase #4	$144.78	13.629%	$164.5121	$164.51	$164.50	$164.50
Purchase #5	$38.78	9.818%	$42.5874	$42.59	$42.60	$42.60
Purchase #6	$35.67	9.744%	$39.1457	$39.15	$39.15	$39.10
Purchase #7	$121.53	11.794%	$135.8632	$135.86	$135.85	$135.90
7 purchase totals =	$700.63		$784.0589	$784.06	$784.05	$784.00