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	$79.30	8.425%	$85.981	$85.98	$86.00	$86.00
Purchase #2	$208.64	3.807%	$216.5829	$216.58	$216.60	$216.60
Purchase #3	$235.50	5.803%	$249.1661	$249.17	$249.15	$249.20
Purchase #4	$82.91	12.449%	$93.2315	$93.23	$93.25	$93.20
Purchase #5	$16.40	10.765%	$18.1655	$18.17	$18.15	$18.20
Purchase #6	$116.72	12.293%	$131.0684	$131.07	$131.05	$131.10
Purchase #7	$240.40	6.189%	$255.2784	$255.28	$255.30	$255.30
7 purchase totals =	$979.87		$1,049.4738	$1,049.48	$1,049.50	$1,049.60