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	$99.87	11.215%	$111.0704	$111.07	$111.05	$111.10
Purchase #2	$30.69	5.651%	$32.4243	$32.42	$32.40	$32.40
Purchase #3	$228.33	12.382%	$256.6018	$256.60	$256.60	$256.60
Purchase #4	$196.79	11.793%	$219.9974	$220.00	$220.00	$220.00
Purchase #5	$217.96	10.480%	$240.8022	$240.80	$240.80	$240.80
Purchase #6	$214.70	8.596%	$233.1556	$233.16	$233.15	$233.20
Purchase #7	$80.46	5.513%	$84.8958	$84.90	$84.90	$84.90
7 purchase totals =	$1,068.80		$1,178.9475	$1,178.95	$1,178.90	$1,179.00