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	$249.47	5.279%	$262.6395	$262.64	$262.65	$262.60
Purchase #2	$178.59	3.238%	$184.3727	$184.37	$184.35	$184.40
Purchase #3	$22.63	11.257%	$25.1775	$25.18	$25.20	$25.20
Purchase #4	$118.57	8.408%	$128.5394	$128.54	$128.55	$128.50
Purchase #5	$163.28	13.216%	$184.8591	$184.86	$184.85	$184.90
Purchase #6	$102.77	8.222%	$111.2197	$111.22	$111.20	$111.20
Purchase #7	$217.31	12.541%	$244.5628	$244.56	$244.55	$244.60
7 purchase totals =	$1,052.62		$1,141.3707	$1,141.37	$1,141.35	$1,141.40