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	$249.27	13.140%	$282.0241	$282.02	$282.00	$282.00
Purchase #2	$118.58	12.450%	$133.3432	$133.34	$133.35	$133.30
Purchase #3	$73.48	11.674%	$82.0581	$82.06	$82.05	$82.10
Purchase #4	$87.73	7.455%	$94.2703	$94.27	$94.25	$94.30
Purchase #5	$34.87	7.832%	$37.601	$37.60	$37.60	$37.60
Purchase #6	$240.49	4.753%	$251.9205	$251.92	$251.90	$251.90
Purchase #7	$158.96	3.236%	$164.1039	$164.10	$164.10	$164.10
7 purchase totals =	$963.38		$1,045.3211	$1,045.31	$1,045.25	$1,045.30