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	$55.39	10.613%	$61.2685	$61.27	$61.25	$61.30
Purchase #2	$84.36	6.533%	$89.8712	$89.87	$89.85	$89.90
Purchase #3	$92.37	12.660%	$104.064	$104.06	$104.05	$104.10
Purchase #4	$171.89	3.722%	$178.2877	$178.29	$178.30	$178.30
Purchase #5	$123.86	9.870%	$136.085	$136.09	$136.10	$136.10
Purchase #6	$128.48	9.734%	$140.9862	$140.99	$141.00	$141.00
Purchase #7	$242.61	9.288%	$265.1436	$265.14	$265.15	$265.10
7 purchase totals =	$898.96		$975.7062	$975.71	$975.70	$975.80