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	$179.58	9.438%	$196.5288	$196.53	$196.55	$196.50
Purchase #2	$59.86	4.264%	$62.4124	$62.41	$62.40	$62.40
Purchase #3	$114.67	11.746%	$128.1391	$128.14	$128.15	$128.10
Purchase #4	$49.39	12.187%	$55.4092	$55.41	$55.40	$55.40
Purchase #5	$112.77	7.288%	$120.9887	$120.99	$121.00	$121.00
Purchase #6	$128.69	11.389%	$143.3465	$143.35	$143.35	$143.30
Purchase #7	$150.38	5.672%	$158.9096	$158.91	$158.90	$158.90
7 purchase totals =	$795.34		$865.7343	$865.74	$865.75	$865.60