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	$199.54	9.803%	$219.1009	$219.10	$219.10	$219.10
Purchase #2	$78.90	8.142%	$85.324	$85.32	$85.30	$85.30
Purchase #3	$139.82	12.207%	$156.8878	$156.89	$156.90	$156.90
Purchase #4	$98.51	13.861%	$112.1645	$112.16	$112.15	$112.20
Purchase #5	$218.59	12.381%	$245.6536	$245.65	$245.65	$245.70
Purchase #6	$52.67	4.145%	$54.8532	$54.85	$54.85	$54.90
Purchase #7	$34.72	6.518%	$36.983	$36.98	$37.00	$37.00
7 purchase totals =	$822.75		$910.9670	$910.95	$910.95	$911.10