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	$156.54	6.693%	$167.0172	$167.02	$167.00	$167.00
Purchase #2	$146.80	10.754%	$162.5869	$162.59	$162.60	$162.60
Purchase #3	$236.94	5.870%	$250.8484	$250.85	$250.85	$250.80
Purchase #4	$56.53	8.330%	$61.2389	$61.24	$61.25	$61.20
Purchase #5	$189.57	8.420%	$205.5318	$205.53	$205.55	$205.50
Purchase #6	$39.83	9.120%	$43.4625	$43.46	$43.45	$43.50
Purchase #7	$118.95	6.284%	$126.4248	$126.42	$126.40	$126.40
7 purchase totals =	$945.16		$1,017.1105	$1,017.11	$1,017.10	$1,017.00