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	$52.82	13.268%	$59.8282	$59.83	$59.85	$59.80
Purchase #2	$109.27	9.619%	$119.7807	$119.78	$119.80	$119.80
Purchase #3	$175.42	12.155%	$196.7423	$196.74	$196.75	$196.70
Purchase #4	$166.26	9.446%	$181.9649	$181.96	$181.95	$182.00
Purchase #5	$207.41	8.207%	$224.4321	$224.43	$224.45	$224.40
Purchase #6	$94.36	3.808%	$97.9532	$97.95	$97.95	$98.00
Purchase #7	$158.52	4.362%	$165.4346	$165.43	$165.45	$165.40
7 purchase totals =	$964.06		$1,046.1360	$1,046.12	$1,046.20	$1,046.10