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	$174.74	9.560%	$191.4451	$191.45	$191.45	$191.40
Purchase #2	$44.78	4.254%	$46.6849	$46.68	$46.70	$46.70
Purchase #3	$150.35	12.678%	$169.4114	$169.41	$169.40	$169.40
Purchase #4	$100.38	13.283%	$113.7135	$113.71	$113.70	$113.70
Purchase #5	$233.51	13.853%	$265.8581	$265.86	$265.85	$265.90
Purchase #6	$190.64	9.147%	$208.0778	$208.08	$208.10	$208.10
Purchase #7	$61.44	8.183%	$66.4676	$66.47	$66.45	$66.50
7 purchase totals =	$955.84		$1,061.6584	$1,061.66	$1,061.65	$1,061.70