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	$182.86	8.785%	$198.9243	$198.92	$198.90	$198.90
Purchase #2	$104.51	12.520%	$117.5947	$117.59	$117.60	$117.60
Purchase #3	$248.53	12.612%	$279.8746	$279.87	$279.85	$279.90
Purchase #4	$192.45	5.743%	$203.5024	$203.50	$203.50	$203.50
Purchase #5	$37.84	13.471%	$42.9374	$42.94	$42.95	$42.90
Purchase #6	$133.58	5.348%	$140.7239	$140.72	$140.70	$140.70
Purchase #7	$188.38	6.654%	$200.9148	$200.91	$200.90	$200.90
7 purchase totals =	$1,088.15		$1,184.4721	$1,184.45	$1,184.40	$1,184.40