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	$11.81	5.275%	$12.433	$12.43	$12.45	$12.40
Purchase #2	$192.66	4.117%	$200.5918	$200.59	$200.60	$200.60
Purchase #3	$90.57	10.696%	$100.2574	$100.26	$100.25	$100.30
Purchase #4	$116.77	7.157%	$125.1272	$125.13	$125.15	$125.10
Purchase #5	$229.64	6.157%	$243.7789	$243.78	$243.80	$243.80
Purchase #6	$146.73	13.424%	$166.427	$166.43	$166.45	$166.40
Purchase #7	$193.71	8.709%	$210.5802	$210.58	$210.60	$210.60
7 purchase totals =	$981.89		$1,059.1955	$1,059.20	$1,059.30	$1,059.20