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	$167.80	11.169%	$186.5416	$186.54	$186.55	$186.50
Purchase #2	$103.40	12.552%	$116.3788	$116.38	$116.40	$116.40
Purchase #3	$140.63	8.299%	$152.3009	$152.30	$152.30	$152.30
Purchase #4	$63.64	3.535%	$65.8897	$65.89	$65.90	$65.90
Purchase #5	$226.38	3.212%	$233.6513	$233.65	$233.65	$233.70
Purchase #6	$171.35	5.297%	$180.4264	$180.43	$180.45	$180.40
Purchase #7	$211.60	4.641%	$221.4204	$221.42	$221.40	$221.40
7 purchase totals =	$1,084.80		$1,156.6091	$1,156.61	$1,156.65	$1,156.60