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	$86.85	11.833%	$97.127	$97.13	$97.15	$97.10
Purchase #2	$206.37	11.166%	$229.4133	$229.41	$229.40	$229.40
Purchase #3	$217.43	8.695%	$236.3355	$236.34	$236.35	$236.30
Purchase #4	$139.79	8.397%	$151.5282	$151.53	$151.55	$151.50
Purchase #5	$137.53	11.178%	$152.9031	$152.90	$152.90	$152.90
Purchase #6	$246.77	12.784%	$278.3171	$278.32	$278.30	$278.30
Purchase #7	$10.56	3.631%	$10.9434	$10.94	$10.95	$10.90
7 purchase totals =	$1,045.30		$1,156.5676	$1,156.57	$1,156.60	$1,156.40