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	$76.69	11.106%	$85.2072	$85.21	$85.20	$85.20
Purchase #2	$195.88	10.537%	$216.5199	$216.52	$216.50	$216.50
Purchase #3	$167.35	10.211%	$184.4381	$184.44	$184.45	$184.40
Purchase #4	$213.78	9.481%	$234.0485	$234.05	$234.05	$234.00
Purchase #5	$18.75	10.727%	$20.7613	$20.76	$20.75	$20.80
Purchase #6	$95.52	10.490%	$105.54	$105.54	$105.55	$105.50
Purchase #7	$198.78	6.804%	$212.305	$212.31	$212.30	$212.30
7 purchase totals =	$966.75		$1,058.8200	$1,058.83	$1,058.80	$1,058.70