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	$139.39	8.871%	$151.7553	$151.76	$151.75	$151.80
Purchase #2	$195.40	11.784%	$218.4259	$218.43	$218.45	$218.40
Purchase #3	$176.89	4.587%	$185.0039	$185.00	$185.00	$185.00
Purchase #4	$98.28	7.869%	$106.0137	$106.01	$106.00	$106.00
Purchase #5	$21.96	10.523%	$24.2709	$24.27	$24.25	$24.30
Purchase #6	$164.38	13.847%	$187.1417	$187.14	$187.15	$187.10
Purchase #7	$168.44	8.477%	$182.7187	$182.72	$182.70	$182.70
7 purchase totals =	$964.74		$1,055.3301	$1,055.33	$1,055.30	$1,055.30