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	$83.63	8.391%	$90.6474	$90.65	$90.65	$90.60
Purchase #2	$180.33	5.436%	$190.1327	$190.13	$190.15	$190.10
Purchase #3	$93.90	10.150%	$103.4309	$103.43	$103.45	$103.40
Purchase #4	$20.33	3.175%	$20.9755	$20.98	$21.00	$21.00
Purchase #5	$185.85	5.241%	$195.5904	$195.59	$195.60	$195.60
Purchase #6	$216.74	7.222%	$232.393	$232.39	$232.40	$232.40
Purchase #7	$203.91	5.696%	$215.5247	$215.52	$215.50	$215.50
7 purchase totals =	$984.69		$1,048.6946	$1,048.69	$1,048.75	$1,048.60