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	$209.28	6.427%	$222.7304	$222.73	$222.75	$222.70
Purchase #2	$36.38	4.350%	$37.9625	$37.96	$37.95	$38.00
Purchase #3	$52.50	8.245%	$56.8286	$56.83	$56.85	$56.80
Purchase #4	$108.64	8.169%	$117.5148	$117.51	$117.50	$117.50
Purchase #5	$174.81	13.786%	$198.9093	$198.91	$198.90	$198.90
Purchase #6	$171.38	5.487%	$180.7836	$180.78	$180.80	$180.80
Purchase #7	$42.90	3.623%	$44.4543	$44.45	$44.45	$44.50
7 purchase totals =	$795.89		$859.1835	$859.17	$859.20	$859.20