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	$43.51	7.853%	$46.9268	$46.93	$46.95	$46.90
Purchase #2	$225.45	13.594%	$256.0977	$256.10	$256.10	$256.10
Purchase #3	$103.84	11.164%	$115.4327	$115.43	$115.45	$115.40
Purchase #4	$64.60	10.549%	$71.4147	$71.41	$71.40	$71.40
Purchase #5	$94.51	6.208%	$100.3772	$100.38	$100.40	$100.40
Purchase #6	$233.55	8.268%	$252.8599	$252.86	$252.85	$252.90
Purchase #7	$223.38	9.850%	$245.3829	$245.38	$245.40	$245.40
7 purchase totals =	$988.84		$1,088.4919	$1,088.49	$1,088.55	$1,088.50