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	$198.43	7.375%	$213.0642	$213.06	$213.05	$213.10
Purchase #2	$31.79	11.549%	$35.4614	$35.46	$35.45	$35.50
Purchase #3	$96.40	9.336%	$105.3999	$105.40	$105.40	$105.40
Purchase #4	$209.79	6.265%	$222.9333	$222.93	$222.95	$222.90
Purchase #5	$91.48	6.595%	$97.5131	$97.51	$97.50	$97.50
Purchase #6	$11.95	12.113%	$13.3975	$13.40	$13.40	$13.40
Purchase #7	$170.38	4.725%	$178.4305	$178.43	$178.45	$178.40
7 purchase totals =	$810.22		$866.1999	$866.19	$866.20	$866.20