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	$164.47	8.171%	$177.9088	$177.91	$177.90	$177.90
Purchase #2	$72.63	8.609%	$78.8827	$78.88	$78.90	$78.90
Purchase #3	$61.25	10.813%	$67.873	$67.87	$67.85	$67.90
Purchase #4	$223.91	4.150%	$233.2023	$233.20	$233.20	$233.20
Purchase #5	$165.78	12.527%	$186.5473	$186.55	$186.55	$186.50
Purchase #6	$189.90	13.365%	$215.2801	$215.28	$215.30	$215.30
Purchase #7	$130.39	6.676%	$139.0948	$139.09	$139.10	$139.10
7 purchase totals =	$1,008.33		$1,098.7890	$1,098.78	$1,098.80	$1,098.80