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	$165.86	12.297%	$186.2558	$186.26	$186.25	$186.30
Purchase #2	$165.73	11.650%	$185.0375	$185.04	$185.05	$185.00
Purchase #3	$34.82	8.600%	$37.8145	$37.81	$37.80	$37.80
Purchase #4	$104.94	12.210%	$117.7532	$117.75	$117.75	$117.80
Purchase #5	$38.90	11.462%	$43.3587	$43.36	$43.35	$43.40
Purchase #6	$164.27	12.176%	$184.2715	$184.27	$184.25	$184.30
Purchase #7	$236.36	13.124%	$267.3799	$267.38	$267.40	$267.40
7 purchase totals =	$910.88		$1,021.8711	$1,021.87	$1,021.85	$1,022.00