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	$63.70	13.159%	$72.0823	$72.08	$72.10	$72.10
Purchase #2	$186.34	5.594%	$196.7639	$196.76	$196.75	$196.80
Purchase #3	$190.60	8.522%	$206.8429	$206.84	$206.85	$206.80
Purchase #4	$247.96	12.544%	$279.0641	$279.06	$279.05	$279.10
Purchase #5	$180.30	11.237%	$200.5603	$200.56	$200.55	$200.60
Purchase #6	$76.78	12.137%	$86.0988	$86.10	$86.10	$86.10
Purchase #7	$39.32	4.681%	$41.1606	$41.16	$41.15	$41.20
7 purchase totals =	$985.00		$1,082.5729	$1,082.56	$1,082.55	$1,082.70