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	$156.33	9.411%	$171.0422	$171.04	$171.05	$171.00
Purchase #2	$87.40	3.529%	$90.4843	$90.48	$90.50	$90.50
Purchase #3	$105.83	5.337%	$111.4781	$111.48	$111.50	$111.50
Purchase #4	$177.90	3.496%	$184.1194	$184.12	$184.10	$184.10
Purchase #5	$105.66	5.320%	$111.2811	$111.28	$111.30	$111.30
Purchase #6	$198.94	13.127%	$225.0549	$225.05	$225.05	$225.10
Purchase #7	$213.28	8.628%	$231.6818	$231.68	$231.70	$231.70
7 purchase totals =	$1,045.34		$1,125.1418	$1,125.13	$1,125.20	$1,125.20