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	$72.51	9.194%	$79.1766	$79.18	$79.20	$79.20
Purchase #2	$110.28	5.477%	$116.32	$116.32	$116.30	$116.30
Purchase #3	$137.30	11.286%	$152.7957	$152.80	$152.80	$152.80
Purchase #4	$242.98	11.377%	$270.6238	$270.62	$270.60	$270.60
Purchase #5	$230.96	12.358%	$259.502	$259.50	$259.50	$259.50
Purchase #6	$101.46	7.665%	$109.2369	$109.24	$109.25	$109.20
Purchase #7	$63.69	5.204%	$67.0044	$67.00	$67.00	$67.00
7 purchase totals =	$959.18		$1,054.6594	$1,054.66	$1,054.65	$1,054.60