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	$48.41	11.762%	$54.104	$54.10	$54.10	$54.10
Purchase #2	$123.98	10.137%	$136.5479	$136.55	$136.55	$136.50
Purchase #3	$94.43	11.512%	$105.3008	$105.30	$105.30	$105.30
Purchase #4	$149.43	5.190%	$157.1854	$157.19	$157.20	$157.20
Purchase #5	$46.27	12.661%	$52.1282	$52.13	$52.15	$52.10
Purchase #6	$135.73	5.766%	$143.5562	$143.56	$143.55	$143.60
Purchase #7	$133.64	8.556%	$145.0742	$145.07	$145.05	$145.10
7 purchase totals =	$731.89		$793.8967	$793.90	$793.90	$793.90