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	$122.58	4.263%	$127.8056	$127.81	$127.80	$127.80
Purchase #2	$168.66	6.268%	$179.2316	$179.23	$179.25	$179.20
Purchase #3	$162.79	7.616%	$175.1881	$175.19	$175.20	$175.20
Purchase #4	$66.49	9.455%	$72.7766	$72.78	$72.80	$72.80
Purchase #5	$166.50	3.638%	$172.5573	$172.56	$172.55	$172.60
Purchase #6	$218.30	7.184%	$233.9827	$233.98	$234.00	$234.00
Purchase #7	$68.85	3.116%	$70.9954	$71.00	$71.00	$71.00
7 purchase totals =	$974.17		$1,032.5373	$1,032.55	$1,032.60	$1,032.60