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	$181.67	10.436%	$200.6291	$200.63	$200.65	$200.60
Purchase #2	$139.79	8.807%	$152.1013	$152.10	$152.10	$152.10
Purchase #3	$85.50	4.498%	$89.3458	$89.35	$89.35	$89.30
Purchase #4	$131.99	3.293%	$136.3364	$136.34	$136.35	$136.30
Purchase #5	$42.70	4.420%	$44.5873	$44.59	$44.60	$44.60
Purchase #6	$161.26	8.506%	$174.9768	$174.98	$175.00	$175.00
Purchase #7	$160.86	13.472%	$182.5311	$182.53	$182.55	$182.50
7 purchase totals =	$903.77		$980.5078	$980.52	$980.60	$980.40