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	$91.53	7.850%	$98.7151	$98.72	$98.70	$98.70
Purchase #2	$171.71	7.810%	$185.1206	$185.12	$185.10	$185.10
Purchase #3	$46.50	6.680%	$49.6062	$49.61	$49.60	$49.60
Purchase #4	$217.48	3.846%	$225.8443	$225.84	$225.85	$225.80
Purchase #5	$11.32	11.531%	$12.6253	$12.63	$12.65	$12.60
Purchase #6	$84.79	5.334%	$89.3127	$89.31	$89.30	$89.30
Purchase #7	$41.94	6.394%	$44.6216	$44.62	$44.60	$44.60
7 purchase totals =	$665.27		$705.8458	$705.85	$705.80	$705.70