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	$43.53	3.112%	$44.8847	$44.88	$44.90	$44.90
Purchase #2	$146.50	4.634%	$153.2888	$153.29	$153.30	$153.30
Purchase #3	$32.88	12.761%	$37.0758	$37.08	$37.10	$37.10
Purchase #4	$244.72	3.774%	$253.9557	$253.96	$253.95	$254.00
Purchase #5	$78.34	9.717%	$85.9523	$85.95	$85.95	$86.00
Purchase #6	$219.50	11.300%	$244.3035	$244.30	$244.30	$244.30
Purchase #7	$45.28	13.504%	$51.3946	$51.39	$51.40	$51.40
7 purchase totals =	$810.75		$870.8554	$870.85	$870.90	$871.00