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	$114.84	4.555%	$120.071	$120.07	$120.05	$120.10
Purchase #2	$116.94	13.355%	$132.5573	$132.56	$132.55	$132.60
Purchase #3	$127.83	7.322%	$137.1897	$137.19	$137.20	$137.20
Purchase #4	$25.90	7.672%	$27.887	$27.89	$27.90	$27.90
Purchase #5	$151.72	8.648%	$164.8407	$164.84	$164.85	$164.80
Purchase #6	$244.94	3.410%	$253.2925	$253.29	$253.30	$253.30
Purchase #7	$228.61	3.858%	$237.4298	$237.43	$237.45	$237.40
7 purchase totals =	$1,010.78		$1,073.2680	$1,073.27	$1,073.30	$1,073.30