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	$187.99	4.628%	$196.6902	$196.69	$196.70	$196.70
Purchase #2	$212.50	8.502%	$230.5668	$230.57	$230.55	$230.60
Purchase #3	$180.99	8.694%	$196.7253	$196.73	$196.75	$196.70
Purchase #4	$82.54	12.223%	$92.6289	$92.63	$92.65	$92.60
Purchase #5	$166.88	10.680%	$184.7028	$184.70	$184.70	$184.70
Purchase #6	$137.78	4.304%	$143.7101	$143.71	$143.70	$143.70
Purchase #7	$118.96	3.484%	$123.1046	$123.10	$123.10	$123.10
7 purchase totals =	$1,087.64		$1,168.1287	$1,168.13	$1,168.15	$1,168.10