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	$79.25	13.275%	$89.7704	$89.77	$89.75	$89.80
Purchase #2	$30.43	8.208%	$32.9277	$32.93	$32.95	$32.90
Purchase #3	$162.76	10.530%	$179.8986	$179.90	$179.90	$179.90
Purchase #4	$14.48	12.470%	$16.2857	$16.29	$16.30	$16.30
Purchase #5	$83.42	10.139%	$91.878	$91.88	$91.90	$91.90
Purchase #6	$188.38	5.833%	$199.3682	$199.37	$199.35	$199.40
Purchase #7	$97.46	4.411%	$101.759	$101.76	$101.75	$101.80
7 purchase totals =	$656.18		$711.8876	$711.90	$711.90	$712.00