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	$41.48	9.371%	$45.3671	$45.37	$45.35	$45.40
Purchase #2	$11.61	10.552%	$12.8351	$12.84	$12.85	$12.80
Purchase #3	$218.71	6.710%	$233.3854	$233.39	$233.40	$233.40
Purchase #4	$143.81	3.293%	$148.5457	$148.55	$148.55	$148.50
Purchase #5	$163.69	9.582%	$179.3748	$179.37	$179.35	$179.40
Purchase #6	$172.96	13.218%	$195.8219	$195.82	$195.80	$195.80
Purchase #7	$52.91	7.697%	$56.9825	$56.98	$57.00	$57.00
7 purchase totals =	$805.17		$872.3125	$872.32	$872.30	$872.30