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	$249.34	5.659%	$263.4502	$263.45	$263.45	$263.50
Purchase #2	$82.32	12.654%	$92.7368	$92.74	$92.75	$92.70
Purchase #3	$107.82	3.697%	$111.8061	$111.81	$111.80	$111.80
Purchase #4	$233.26	4.411%	$243.5491	$243.55	$243.55	$243.50
Purchase #5	$168.92	4.109%	$175.8609	$175.86	$175.85	$175.90
Purchase #6	$244.59	3.153%	$252.3019	$252.30	$252.30	$252.30
Purchase #7	$238.29	9.802%	$261.6472	$261.65	$261.65	$261.60
7 purchase totals =	$1,324.54		$1,401.3522	$1,401.36	$1,401.35	$1,401.30