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	$129.25	11.393%	$143.9755	$143.98	$144.00	$144.00
Purchase #2	$182.73	10.452%	$201.8289	$201.83	$201.85	$201.80
Purchase #3	$226.77	10.812%	$251.2884	$251.29	$251.30	$251.30
Purchase #4	$209.35	11.574%	$233.5802	$233.58	$233.60	$233.60
Purchase #5	$128.25	11.411%	$142.8846	$142.88	$142.90	$142.90
Purchase #6	$54.89	6.770%	$58.6061	$58.61	$58.60	$58.60
Purchase #7	$47.30	11.294%	$52.6421	$52.64	$52.65	$52.60
7 purchase totals =	$978.54		$1,084.8058	$1,084.81	$1,084.90	$1,084.80