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	$177.89	12.158%	$199.5179	$199.52	$199.50	$199.50
Purchase #2	$155.48	13.686%	$176.759	$176.76	$176.75	$176.80
Purchase #3	$131.55	11.109%	$146.1639	$146.16	$146.15	$146.20
Purchase #4	$83.92	6.457%	$89.3387	$89.34	$89.35	$89.30
Purchase #5	$193.81	11.276%	$215.664	$215.66	$215.65	$215.70
Purchase #6	$95.89	6.263%	$101.8956	$101.90	$101.90	$101.90
Purchase #7	$238.60	9.410%	$261.0523	$261.05	$261.05	$261.10
7 purchase totals =	$1,077.14		$1,190.3914	$1,190.39	$1,190.35	$1,190.50