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	$54.63	8.829%	$59.4533	$59.45	$59.45	$59.50
Purchase #2	$93.66	6.301%	$99.5615	$99.56	$99.55	$99.60
Purchase #3	$233.69	9.803%	$256.5986	$256.60	$256.60	$256.60
Purchase #4	$221.76	9.116%	$241.9756	$241.98	$242.00	$242.00
Purchase #5	$30.40	13.573%	$34.5262	$34.53	$34.55	$34.50
Purchase #6	$216.78	6.411%	$230.6778	$230.68	$230.70	$230.70
Purchase #7	$103.37	10.822%	$114.5567	$114.56	$114.55	$114.60
7 purchase totals =	$954.29		$1,037.3497	$1,037.36	$1,037.40	$1,037.50