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	$218.84	6.220%	$232.4518	$232.45	$232.45	$232.50
Purchase #2	$53.67	11.602%	$59.8968	$59.90	$59.90	$59.90
Purchase #3	$164.66	6.545%	$175.437	$175.44	$175.45	$175.40
Purchase #4	$38.83	9.270%	$42.4295	$42.43	$42.45	$42.40
Purchase #5	$154.91	4.147%	$161.3341	$161.33	$161.35	$161.30
Purchase #6	$141.66	4.124%	$147.5021	$147.50	$147.50	$147.50
Purchase #7	$204.75	10.154%	$225.5403	$225.54	$225.55	$225.50
7 purchase totals =	$977.32		$1,044.5916	$1,044.59	$1,044.65	$1,044.50