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	$147.30	13.381%	$167.0102	$167.01	$167.00	$167.00
Purchase #2	$68.35	4.124%	$71.1688	$71.17	$71.15	$71.20
Purchase #3	$244.99	12.762%	$276.2556	$276.26	$276.25	$276.30
Purchase #4	$184.37	11.266%	$205.1411	$205.14	$205.15	$205.10
Purchase #5	$238.51	13.631%	$271.0213	$271.02	$271.00	$271.00
Purchase #6	$162.94	3.308%	$168.3301	$168.33	$168.35	$168.30
Purchase #7	$36.34	3.445%	$37.5919	$37.59	$37.60	$37.60
7 purchase totals =	$1,082.80		$1,196.5190	$1,196.52	$1,196.50	$1,196.50