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	$76.82	7.561%	$82.6284	$82.63	$82.65	$82.60
Purchase #2	$111.27	4.330%	$116.088	$116.09	$116.10	$116.10
Purchase #3	$101.41	10.501%	$112.0591	$112.06	$112.05	$112.10
Purchase #4	$134.41	11.734%	$150.1817	$150.18	$150.20	$150.20
Purchase #5	$79.37	3.778%	$82.3686	$82.37	$82.35	$82.40
Purchase #6	$250.44	7.304%	$268.7321	$268.73	$268.75	$268.70
Purchase #7	$202.55	5.554%	$213.7996	$213.80	$213.80	$213.80
7 purchase totals =	$956.27		$1,025.8575	$1,025.86	$1,025.90	$1,025.90