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	$125.94	11.639%	$140.5982	$140.60	$140.60	$140.60
Purchase #2	$137.54	7.377%	$147.6863	$147.69	$147.70	$147.70
Purchase #3	$73.98	6.459%	$78.7584	$78.76	$78.75	$78.80
Purchase #4	$163.51	9.816%	$179.5601	$179.56	$179.55	$179.60
Purchase #5	$67.35	10.444%	$74.384	$74.38	$74.40	$74.40
Purchase #6	$148.65	9.243%	$162.3897	$162.39	$162.40	$162.40
Purchase #7	$95.67	10.544%	$105.7574	$105.76	$105.75	$105.80
7 purchase totals =	$812.64		$889.1341	$889.14	$889.15	$889.30