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	$93.46	5.779%	$98.8611	$98.86	$98.85	$98.90
Purchase #2	$198.42	6.133%	$210.5891	$210.59	$210.60	$210.60
Purchase #3	$184.61	8.261%	$199.8606	$199.86	$199.85	$199.90
Purchase #4	$52.60	10.578%	$58.164	$58.16	$58.15	$58.20
Purchase #5	$201.84	8.872%	$219.7472	$219.75	$219.75	$219.70
Purchase #6	$123.60	3.229%	$127.591	$127.59	$127.60	$127.60
Purchase #7	$179.32	4.189%	$186.8317	$186.83	$186.85	$186.80
7 purchase totals =	$1,033.85		$1,101.6447	$1,101.64	$1,101.65	$1,101.70