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	$44.67	12.475%	$50.2426	$50.24	$50.25	$50.20
Purchase #2	$117.52	4.700%	$123.0434	$123.04	$123.05	$123.00
Purchase #3	$184.27	7.743%	$198.538	$198.54	$198.55	$198.50
Purchase #4	$96.58	11.858%	$108.0325	$108.03	$108.05	$108.00
Purchase #5	$179.49	5.168%	$188.766	$188.77	$188.75	$188.80
Purchase #6	$200.63	11.366%	$223.4336	$223.43	$223.45	$223.40
Purchase #7	$133.84	7.448%	$143.8084	$143.81	$143.80	$143.80
7 purchase totals =	$957.00		$1,035.8645	$1,035.86	$1,035.90	$1,035.70