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	$126.64	13.373%	$143.5756	$143.58	$143.60	$143.60
Purchase #2	$144.27	11.293%	$160.5624	$160.56	$160.55	$160.60
Purchase #3	$38.88	6.818%	$41.5308	$41.53	$41.55	$41.50
Purchase #4	$246.91	3.533%	$255.6333	$255.63	$255.65	$255.60
Purchase #5	$115.82	5.815%	$122.5549	$122.55	$122.55	$122.60
Purchase #6	$139.54	12.112%	$156.4411	$156.44	$156.45	$156.40
Purchase #7	$194.82	8.451%	$211.2842	$211.28	$211.30	$211.30
7 purchase totals =	$1,006.88		$1,091.5823	$1,091.57	$1,091.65	$1,091.60