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	$127.47	10.481%	$140.8301	$140.83	$140.85	$140.80
Purchase #2	$143.48	5.455%	$151.3068	$151.31	$151.30	$151.30
Purchase #3	$31.44	13.722%	$35.7542	$35.75	$35.75	$35.80
Purchase #4	$133.90	5.356%	$141.0717	$141.07	$141.05	$141.10
Purchase #5	$250.82	12.289%	$281.6433	$281.64	$281.65	$281.60
Purchase #6	$131.79	13.700%	$149.8452	$149.85	$149.85	$149.80
Purchase #7	$39.63	9.473%	$43.3841	$43.38	$43.40	$43.40
7 purchase totals =	$858.53		$943.8354	$943.83	$943.85	$943.80