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	$200.73	11.415%	$223.6433	$223.64	$223.65	$223.60
Purchase #2	$56.99	8.187%	$61.6558	$61.66	$61.65	$61.70
Purchase #3	$160.32	8.202%	$173.4694	$173.47	$173.45	$173.50
Purchase #4	$100.55	13.302%	$113.9252	$113.93	$113.95	$113.90
Purchase #5	$130.98	9.705%	$143.6916	$143.69	$143.70	$143.70
Purchase #6	$153.99	5.422%	$162.3393	$162.34	$162.35	$162.30
Purchase #7	$245.82	7.342%	$263.8681	$263.87	$263.85	$263.90
7 purchase totals =	$1,049.38		$1,142.5927	$1,142.60	$1,142.60	$1,142.60