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	$45.66	5.860%	$48.3357	$48.34	$48.35	$48.30
Purchase #2	$150.90	11.644%	$168.4708	$168.47	$168.45	$168.50
Purchase #3	$10.41	4.709%	$10.9002	$10.90	$10.90	$10.90
Purchase #4	$248.76	4.413%	$259.7378	$259.74	$259.75	$259.70
Purchase #5	$102.54	13.560%	$116.4444	$116.44	$116.45	$116.40
Purchase #6	$236.77	13.462%	$268.644	$268.64	$268.65	$268.60
Purchase #7	$137.52	5.483%	$145.0602	$145.06	$145.05	$145.10
7 purchase totals =	$932.56		$1,017.5931	$1,017.59	$1,017.60	$1,017.50