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	$218.55	4.178%	$227.681	$227.68	$227.70	$227.70
Purchase #2	$168.46	7.697%	$181.4264	$181.43	$181.45	$181.40
Purchase #3	$34.94	13.154%	$39.536	$39.54	$39.55	$39.50
Purchase #4	$244.34	6.229%	$259.5599	$259.56	$259.55	$259.60
Purchase #5	$87.45	7.501%	$94.0096	$94.01	$94.00	$94.00
Purchase #6	$113.25	12.623%	$127.5455	$127.55	$127.55	$127.50
Purchase #7	$115.41	4.552%	$120.6635	$120.66	$120.65	$120.70
7 purchase totals =	$982.40		$1,050.4219	$1,050.43	$1,050.45	$1,050.40