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	$63.28	3.855%	$65.7194	$65.72	$65.70	$65.70
Purchase #2	$238.93	9.393%	$261.3727	$261.37	$261.35	$261.40
Purchase #3	$235.72	12.535%	$265.2675	$265.27	$265.25	$265.30
Purchase #4	$110.98	4.589%	$116.0729	$116.07	$116.05	$116.10
Purchase #5	$154.85	11.382%	$172.475	$172.48	$172.50	$172.50
Purchase #6	$233.99	3.237%	$241.5643	$241.56	$241.55	$241.60
Purchase #7	$206.49	8.417%	$223.8703	$223.87	$223.85	$223.90
7 purchase totals =	$1,244.24		$1,346.3421	$1,346.34	$1,346.25	$1,346.50