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	$209.61	8.841%	$228.1416	$228.14	$228.15	$228.10
Purchase #2	$31.98	5.372%	$33.698	$33.70	$33.70	$33.70
Purchase #3	$67.98	6.583%	$72.4551	$72.46	$72.45	$72.50
Purchase #4	$69.84	12.357%	$78.4701	$78.47	$78.45	$78.50
Purchase #5	$130.64	11.779%	$146.0281	$146.03	$146.05	$146.00
Purchase #6	$131.85	10.432%	$145.6046	$145.60	$145.60	$145.60
Purchase #7	$203.60	4.450%	$212.6602	$212.66	$212.65	$212.70
7 purchase totals =	$845.50		$917.0577	$917.06	$917.05	$917.10