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	$203.53	5.239%	$214.1929	$214.19	$214.20	$214.20
Purchase #2	$69.79	12.444%	$78.4747	$78.47	$78.45	$78.50
Purchase #3	$223.64	4.510%	$233.7262	$233.73	$233.75	$233.70
Purchase #4	$45.89	3.484%	$47.4888	$47.49	$47.50	$47.50
Purchase #5	$25.95	6.496%	$27.6357	$27.64	$27.65	$27.60
Purchase #6	$132.55	7.212%	$142.1095	$142.11	$142.10	$142.10
Purchase #7	$226.50	3.672%	$234.8171	$234.82	$234.80	$234.80
7 purchase totals =	$927.85		$978.4449	$978.45	$978.45	$978.40