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	$139.51	9.295%	$152.4775	$152.48	$152.50	$152.50
Purchase #2	$225.86	7.814%	$243.5087	$243.51	$243.50	$243.50
Purchase #3	$70.42	11.589%	$78.581	$78.58	$78.60	$78.60
Purchase #4	$245.90	3.159%	$253.668	$253.67	$253.65	$253.70
Purchase #5	$46.74	9.141%	$51.0125	$51.01	$51.00	$51.00
Purchase #6	$42.46	3.164%	$43.8034	$43.80	$43.80	$43.80
Purchase #7	$210.57	3.694%	$218.3485	$218.35	$218.35	$218.30
7 purchase totals =	$981.46		$1,041.3996	$1,041.40	$1,041.40	$1,041.40