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	$162.39	12.219%	$182.2324	$182.23	$182.25	$182.20
Purchase #2	$196.40	9.582%	$215.219	$215.22	$215.20	$215.20
Purchase #3	$28.29	4.375%	$29.5277	$29.53	$29.55	$29.50
Purchase #4	$224.96	11.318%	$250.421	$250.42	$250.40	$250.40
Purchase #5	$95.71	10.424%	$105.6868	$105.69	$105.70	$105.70
Purchase #6	$93.51	12.238%	$104.9538	$104.95	$104.95	$105.00
Purchase #7	$108.89	3.330%	$112.516	$112.52	$112.50	$112.50
7 purchase totals =	$910.15		$1,000.5567	$1,000.56	$1,000.55	$1,000.50