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	$80.62	7.694%	$86.8229	$86.82	$86.80	$86.80
Purchase #2	$29.79	6.255%	$31.6534	$31.65	$31.65	$31.70
Purchase #3	$11.72	9.722%	$12.8594	$12.86	$12.85	$12.90
Purchase #4	$214.91	13.706%	$244.3656	$244.37	$244.35	$244.40
Purchase #5	$211.66	4.413%	$221.0006	$221.00	$221.00	$221.00
Purchase #6	$216.85	7.839%	$233.8489	$233.85	$233.85	$233.80
Purchase #7	$56.66	4.860%	$59.4137	$59.41	$59.40	$59.40
7 purchase totals =	$822.21		$889.9645	$889.96	$889.90	$890.00