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	$150.39	9.207%	$164.2364	$164.24	$164.25	$164.20
Purchase #2	$106.56	7.318%	$114.3581	$114.36	$114.35	$114.40
Purchase #3	$5.56	5.278%	$5.8535	$5.85	$5.85	$5.90
Purchase #4	$221.34	11.411%	$246.5971	$246.60	$246.60	$246.60
Purchase #5	$137.53	9.406%	$150.4661	$150.47	$150.45	$150.50
Purchase #6	$137.54	13.627%	$156.2826	$156.28	$156.30	$156.30
Purchase #7	$221.25	11.861%	$247.4925	$247.49	$247.50	$247.50
7 purchase totals =	$980.17		$1,085.2863	$1,085.29	$1,085.30	$1,085.40