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	$184.98	11.362%	$205.9974	$206.00	$206.00	$206.00
Purchase #2	$73.45	9.435%	$80.38	$80.38	$80.40	$80.40
Purchase #3	$156.82	5.569%	$165.5533	$165.55	$165.55	$165.60
Purchase #4	$32.87	4.814%	$34.4524	$34.45	$34.45	$34.50
Purchase #5	$166.33	9.393%	$181.9534	$181.95	$181.95	$182.00
Purchase #6	$230.90	13.703%	$262.5402	$262.54	$262.55	$262.50
Purchase #7	$64.54	11.536%	$71.9853	$71.99	$72.00	$72.00
7 purchase totals =	$909.89		$1,002.8620	$1,002.86	$1,002.90	$1,003.00