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	$73.44	9.652%	$80.5284	$80.53	$80.55	$80.50
Purchase #2	$179.60	3.319%	$185.5609	$185.56	$185.55	$185.60
Purchase #3	$125.82	11.531%	$140.3283	$140.33	$140.35	$140.30
Purchase #4	$135.35	7.577%	$145.6055	$145.61	$145.60	$145.60
Purchase #5	$151.29	11.359%	$168.475	$168.48	$168.50	$168.50
Purchase #6	$205.61	10.303%	$226.794	$226.79	$226.80	$226.80
Purchase #7	$134.65	10.355%	$148.593	$148.59	$148.60	$148.60
7 purchase totals =	$1,005.76		$1,095.8851	$1,095.89	$1,095.95	$1,095.90