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	$186.26	10.765%	$206.3109	$206.31	$206.30	$206.30
Purchase #2	$153.65	5.627%	$162.2959	$162.30	$162.30	$162.30
Purchase #3	$92.96	12.150%	$104.2546	$104.25	$104.25	$104.30
Purchase #4	$73.78	6.254%	$78.3942	$78.39	$78.40	$78.40
Purchase #5	$146.67	7.327%	$157.4165	$157.42	$157.40	$157.40
Purchase #6	$135.48	11.333%	$150.8339	$150.83	$150.85	$150.80
Purchase #7	$232.69	8.194%	$251.7566	$251.76	$251.75	$251.80
7 purchase totals =	$1,021.49		$1,111.2626	$1,111.26	$1,111.25	$1,111.30