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	$196.56	10.593%	$217.3816	$217.38	$217.40	$217.40
Purchase #2	$138.72	13.394%	$157.3002	$157.30	$157.30	$157.30
Purchase #3	$138.48	6.516%	$147.5034	$147.50	$147.50	$147.50
Purchase #4	$213.84	11.405%	$238.2285	$238.23	$238.25	$238.20
Purchase #5	$95.77	3.476%	$99.099	$99.10	$99.10	$99.10
Purchase #6	$239.58	3.460%	$247.8695	$247.87	$247.85	$247.90
Purchase #7	$64.88	12.609%	$73.0607	$73.06	$73.05	$73.10
7 purchase totals =	$1,087.83		$1,180.4429	$1,180.44	$1,180.45	$1,180.50