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	$58.85	11.415%	$65.5677	$65.57	$65.55	$65.60
Purchase #2	$78.30	9.589%	$85.8082	$85.81	$85.80	$85.80
Purchase #3	$12.87	11.498%	$14.3498	$14.35	$14.35	$14.30
Purchase #4	$87.52	10.766%	$96.9424	$96.94	$96.95	$96.90
Purchase #5	$219.60	5.539%	$231.7636	$231.76	$231.75	$231.80
Purchase #6	$213.41	9.607%	$233.9123	$233.91	$233.90	$233.90
Purchase #7	$112.88	5.267%	$118.8254	$118.83	$118.85	$118.80
7 purchase totals =	$783.43		$847.1694	$847.17	$847.15	$847.10