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	$112.98	12.869%	$127.5194	$127.52	$127.50	$127.50
Purchase #2	$192.98	5.290%	$203.1886	$203.19	$203.20	$203.20
Purchase #3	$58.86	5.777%	$62.2603	$62.26	$62.25	$62.30
Purchase #4	$112.85	6.116%	$119.7519	$119.75	$119.75	$119.80
Purchase #5	$143.54	4.862%	$150.5189	$150.52	$150.50	$150.50
Purchase #6	$249.50	12.389%	$280.4106	$280.41	$280.40	$280.40
Purchase #7	$149.45	6.826%	$159.6515	$159.65	$159.65	$159.70
7 purchase totals =	$1,020.16		$1,103.3012	$1,103.30	$1,103.25	$1,103.40