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	$113.57	3.869%	$117.964	$117.96	$117.95	$118.00
Purchase #2	$138.89	3.250%	$143.4039	$143.40	$143.40	$143.40
Purchase #3	$91.55	6.472%	$97.4751	$97.48	$97.50	$97.50
Purchase #4	$40.55	6.657%	$43.2494	$43.25	$43.25	$43.20
Purchase #5	$48.64	11.309%	$54.1407	$54.14	$54.15	$54.10
Purchase #6	$228.79	12.258%	$256.8351	$256.84	$256.85	$256.80
Purchase #7	$68.39	7.264%	$73.3578	$73.36	$73.35	$73.40
7 purchase totals =	$730.38		$786.4260	$786.43	$786.45	$786.40