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	$148.46	13.826%	$168.9861	$168.99	$169.00	$169.00
Purchase #2	$48.99	12.418%	$55.0736	$55.07	$55.05	$55.10
Purchase #3	$57.78	3.728%	$59.934	$59.93	$59.95	$59.90
Purchase #4	$36.73	3.688%	$38.0846	$38.08	$38.10	$38.10
Purchase #5	$203.44	9.600%	$222.9702	$222.97	$222.95	$223.00
Purchase #6	$76.35	6.864%	$81.5907	$81.59	$81.60	$81.60
Purchase #7	$134.46	13.706%	$152.8891	$152.89	$152.90	$152.90
7 purchase totals =	$706.21		$779.5283	$779.52	$779.55	$779.60