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	$233.52	6.570%	$248.8623	$248.86	$248.85	$248.90
Purchase #2	$54.45	6.321%	$57.8918	$57.89	$57.90	$57.90
Purchase #3	$210.90	11.182%	$234.4828	$234.48	$234.50	$234.50
Purchase #4	$113.37	9.534%	$124.1787	$124.18	$124.20	$124.20
Purchase #5	$91.84	10.584%	$101.5603	$101.56	$101.55	$101.60
Purchase #6	$68.54	4.721%	$71.7758	$71.78	$71.80	$71.80
Purchase #7	$234.29	4.393%	$244.5824	$244.58	$244.60	$244.60
7 purchase totals =	$1,006.91		$1,083.3341	$1,083.33	$1,083.40	$1,083.50