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	$235.39	7.592%	$253.2608	$253.26	$253.25	$253.30
Purchase #2	$148.85	3.667%	$154.3083	$154.31	$154.30	$154.30
Purchase #3	$105.34	6.614%	$112.3072	$112.31	$112.30	$112.30
Purchase #4	$135.34	4.442%	$141.3518	$141.35	$141.35	$141.40
Purchase #5	$78.55	4.732%	$82.267	$82.27	$82.25	$82.30
Purchase #6	$149.76	4.758%	$156.8856	$156.89	$156.90	$156.90
Purchase #7	$106.76	8.815%	$116.1709	$116.17	$116.15	$116.20
7 purchase totals =	$959.99		$1,016.5516	$1,016.56	$1,016.50	$1,016.70