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	$170.38	3.630%	$176.5648	$176.56	$176.55	$176.60
Purchase #2	$23.83	3.255%	$24.6057	$24.61	$24.60	$24.60
Purchase #3	$41.31	3.145%	$42.6092	$42.61	$42.60	$42.60
Purchase #4	$29.71	10.755%	$32.9053	$32.91	$32.90	$32.90
Purchase #5	$240.65	10.720%	$266.4477	$266.45	$266.45	$266.40
Purchase #6	$126.75	3.731%	$131.479	$131.48	$131.50	$131.50
Purchase #7	$109.27	11.218%	$121.5279	$121.53	$121.55	$121.50
7 purchase totals =	$741.90		$796.1396	$796.15	$796.15	$796.10