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	$236.82	12.121%	$265.525	$265.53	$265.55	$265.50
Purchase #2	$237.80	8.153%	$257.1878	$257.19	$257.20	$257.20
Purchase #3	$196.96	4.141%	$205.1161	$205.12	$205.10	$205.10
Purchase #4	$200.35	7.750%	$215.8771	$215.88	$215.90	$215.90
Purchase #5	$58.68	4.315%	$61.212	$61.21	$61.20	$61.20
Purchase #6	$47.46	10.723%	$52.5491	$52.55	$52.55	$52.50
Purchase #7	$56.85	5.224%	$59.8198	$59.82	$59.80	$59.80
7 purchase totals =	$1,034.92		$1,117.2869	$1,117.30	$1,117.30	$1,117.20