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	$177.96	7.614%	$191.5099	$191.51	$191.50	$191.50
Purchase #2	$164.90	12.455%	$185.4383	$185.44	$185.45	$185.40
Purchase #3	$49.59	7.819%	$53.4674	$53.47	$53.45	$53.50
Purchase #4	$81.89	9.436%	$89.6171	$89.62	$89.60	$89.60
Purchase #5	$39.35	13.473%	$44.6516	$44.65	$44.65	$44.70
Purchase #6	$16.59	5.704%	$17.5363	$17.54	$17.55	$17.50
Purchase #7	$110.29	11.540%	$123.0175	$123.02	$123.00	$123.00
7 purchase totals =	$640.57		$705.2381	$705.25	$705.20	$705.20