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	$8.73	10.322%	$9.6311	$9.63	$9.65	$9.60
Purchase #2	$41.48	4.795%	$43.469	$43.47	$43.45	$43.50
Purchase #3	$82.87	3.490%	$85.7622	$85.76	$85.75	$85.80
Purchase #4	$194.67	13.822%	$221.5773	$221.58	$221.60	$221.60
Purchase #5	$78.55	6.598%	$83.7327	$83.73	$83.75	$83.70
Purchase #6	$151.49	13.448%	$171.8624	$171.86	$171.85	$171.90
Purchase #7	$34.60	13.860%	$39.3956	$39.40	$39.40	$39.40
7 purchase totals =	$592.39		$655.4303	$655.43	$655.45	$655.50