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	$30.30	6.422%	$32.2459	$32.25	$32.25	$32.20
Purchase #2	$59.63	4.741%	$62.4571	$62.46	$62.45	$62.50
Purchase #3	$238.94	10.653%	$264.3943	$264.39	$264.40	$264.40
Purchase #4	$39.57	11.575%	$44.1502	$44.15	$44.15	$44.20
Purchase #5	$163.92	4.692%	$171.6111	$171.61	$171.60	$171.60
Purchase #6	$163.32	11.295%	$181.767	$181.77	$181.75	$181.80
Purchase #7	$5.88	11.651%	$6.5651	$6.57	$6.55	$6.60
7 purchase totals =	$701.56		$763.1907	$763.20	$763.15	$763.30