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	$39.65	8.328%	$42.9521	$42.95	$42.95	$43.00
Purchase #2	$181.62	10.405%	$200.5176	$200.52	$200.50	$200.50
Purchase #3	$124.38	6.313%	$132.2321	$132.23	$132.25	$132.20
Purchase #4	$220.53	8.137%	$238.4745	$238.47	$238.45	$238.50
Purchase #5	$179.26	4.464%	$187.2622	$187.26	$187.25	$187.30
Purchase #6	$115.29	10.645%	$127.5626	$127.56	$127.55	$127.60
Purchase #7	$122.52	3.815%	$127.1941	$127.19	$127.20	$127.20
7 purchase totals =	$983.25		$1,056.1952	$1,056.18	$1,056.15	$1,056.30