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	$146.42	11.287%	$162.9464	$162.95	$162.95	$162.90
Purchase #2	$38.60	12.319%	$43.3551	$43.36	$43.35	$43.40
Purchase #3	$229.90	6.301%	$244.386	$244.39	$244.40	$244.40
Purchase #4	$159.39	9.741%	$174.9162	$174.92	$174.90	$174.90
Purchase #5	$180.37	3.687%	$187.0202	$187.02	$187.00	$187.00
Purchase #6	$21.83	4.150%	$22.7359	$22.74	$22.75	$22.70
Purchase #7	$25.47	8.208%	$27.5606	$27.56	$27.55	$27.60
7 purchase totals =	$801.98		$862.9204	$862.94	$862.90	$862.90