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	$54.40	9.545%	$59.5925	$59.59	$59.60	$59.60
Purchase #2	$200.80	8.181%	$217.2274	$217.23	$217.25	$217.20
Purchase #3	$96.93	12.702%	$109.242	$109.24	$109.25	$109.20
Purchase #4	$202.40	4.311%	$211.1255	$211.13	$211.15	$211.10
Purchase #5	$127.83	13.539%	$145.1369	$145.14	$145.15	$145.10
Purchase #6	$129.46	8.262%	$140.156	$140.16	$140.15	$140.20
Purchase #7	$140.62	8.710%	$152.868	$152.87	$152.85	$152.90
7 purchase totals =	$952.44		$1,035.3483	$1,035.36	$1,035.40	$1,035.30