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	$185.58	5.691%	$196.1414	$196.14	$196.15	$196.10
Purchase #2	$26.67	3.260%	$27.5394	$27.54	$27.55	$27.50
Purchase #3	$71.37	9.218%	$77.9489	$77.95	$77.95	$77.90
Purchase #4	$213.72	6.478%	$227.5648	$227.56	$227.55	$227.60
Purchase #5	$63.72	5.430%	$67.18	$67.18	$67.20	$67.20
Purchase #6	$113.70	11.874%	$127.2007	$127.20	$127.20	$127.20
Purchase #7	$17.64	7.352%	$18.9369	$18.94	$18.95	$18.90
7 purchase totals =	$692.40		$742.5121	$742.51	$742.55	$742.40