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	$73.57	6.528%	$78.3726	$78.37	$78.35	$78.40
Purchase #2	$10.63	7.815%	$11.4607	$11.46	$11.45	$11.50
Purchase #3	$44.32	12.117%	$49.6903	$49.69	$49.70	$49.70
Purchase #4	$144.26	13.846%	$164.2342	$164.23	$164.25	$164.20
Purchase #5	$114.91	7.344%	$123.349	$123.35	$123.35	$123.30
Purchase #6	$100.52	10.792%	$111.3681	$111.37	$111.35	$111.40
Purchase #7	$148.34	8.201%	$160.5054	$160.51	$160.50	$160.50
7 purchase totals =	$636.55		$698.9803	$698.98	$698.95	$699.00