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	$182.25	13.308%	$206.5038	$206.50	$206.50	$206.50
Purchase #2	$131.56	10.523%	$145.4041	$145.40	$145.40	$145.40
Purchase #3	$123.63	10.586%	$136.7175	$136.72	$136.70	$136.70
Purchase #4	$201.89	4.350%	$210.6722	$210.67	$210.65	$210.70
Purchase #5	$33.99	12.518%	$38.2449	$38.24	$38.25	$38.20
Purchase #6	$96.52	4.848%	$101.1993	$101.20	$101.20	$101.20
Purchase #7	$181.98	7.794%	$196.1635	$196.16	$196.15	$196.20
7 purchase totals =	$951.82		$1,034.9053	$1,034.89	$1,034.85	$1,034.90