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	$174.53	12.341%	$196.0687	$196.07	$196.05	$196.10
Purchase #2	$134.91	6.527%	$143.7156	$143.72	$143.70	$143.70
Purchase #3	$81.65	5.320%	$85.9938	$85.99	$86.00	$86.00
Purchase #4	$232.56	6.129%	$246.8136	$246.81	$246.80	$246.80
Purchase #5	$186.48	7.705%	$200.8483	$200.85	$200.85	$200.80
Purchase #6	$56.83	9.733%	$62.3613	$62.36	$62.35	$62.40
Purchase #7	$101.27	3.703%	$105.02	$105.02	$105.00	$105.00
7 purchase totals =	$968.23		$1,040.8213	$1,040.82	$1,040.75	$1,040.80