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	$230.83	13.455%	$261.8882	$261.89	$261.90	$261.90
Purchase #2	$246.82	11.649%	$275.5721	$275.57	$275.55	$275.60
Purchase #3	$91.98	9.706%	$100.9076	$100.91	$100.90	$100.90
Purchase #4	$159.65	3.249%	$164.837	$164.84	$164.85	$164.80
Purchase #5	$158.57	6.807%	$169.3639	$169.36	$169.35	$169.40
Purchase #6	$245.57	7.446%	$263.8551	$263.86	$263.85	$263.90
Purchase #7	$163.85	9.757%	$179.8368	$179.84	$179.85	$179.80
7 purchase totals =	$1,297.27		$1,416.2607	$1,416.27	$1,416.25	$1,416.30