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	$148.46	9.678%	$162.828	$162.83	$162.85	$162.80
Purchase #2	$247.82	13.648%	$281.6425	$281.64	$281.65	$281.60
Purchase #3	$225.80	11.778%	$252.3947	$252.39	$252.40	$252.40
Purchase #4	$139.39	9.715%	$152.9317	$152.93	$152.95	$152.90
Purchase #5	$110.86	11.314%	$123.4027	$123.40	$123.40	$123.40
Purchase #6	$38.96	3.351%	$40.2655	$40.27	$40.25	$40.30
Purchase #7	$235.42	6.731%	$251.2661	$251.27	$251.25	$251.30
7 purchase totals =	$1,146.71		$1,264.7312	$1,264.73	$1,264.75	$1,264.70