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	$176.81	4.330%	$184.4659	$184.47	$184.45	$184.50
Purchase #2	$36.87	4.526%	$38.5387	$38.54	$38.55	$38.50
Purchase #3	$32.52	6.402%	$34.6019	$34.60	$34.60	$34.60
Purchase #4	$40.53	3.249%	$41.8468	$41.85	$41.85	$41.80
Purchase #5	$216.55	4.852%	$227.057	$227.06	$227.05	$227.10
Purchase #6	$40.35	13.410%	$45.7609	$45.76	$45.75	$45.80
Purchase #7	$143.90	4.457%	$150.3136	$150.31	$150.30	$150.30
7 purchase totals =	$687.53		$722.5848	$722.59	$722.55	$722.60