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	$233.51	13.737%	$265.5873	$265.59	$265.60	$265.60
Purchase #2	$131.35	3.720%	$136.2362	$136.24	$136.25	$136.20
Purchase #3	$165.61	4.651%	$173.3125	$173.31	$173.30	$173.30
Purchase #4	$102.82	6.344%	$109.3429	$109.34	$109.35	$109.30
Purchase #5	$40.31	7.685%	$43.4078	$43.41	$43.40	$43.40
Purchase #6	$222.43	12.208%	$249.5843	$249.58	$249.60	$249.60
Purchase #7	$201.94	5.557%	$213.1618	$213.16	$213.15	$213.20
7 purchase totals =	$1,097.97		$1,190.6328	$1,190.63	$1,190.65	$1,190.60