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	$186.40	3.796%	$193.4757	$193.48	$193.50	$193.50
Purchase #2	$35.83	9.524%	$39.2424	$39.24	$39.25	$39.20
Purchase #3	$133.67	6.633%	$142.5363	$142.54	$142.55	$142.50
Purchase #4	$97.49	3.108%	$100.52	$100.52	$100.50	$100.50
Purchase #5	$143.85	9.841%	$158.0063	$158.01	$158.00	$158.00
Purchase #6	$153.27	9.873%	$168.4023	$168.40	$168.40	$168.40
Purchase #7	$154.90	10.261%	$170.7943	$170.79	$170.80	$170.80
7 purchase totals =	$905.41		$972.9773	$972.98	$973.00	$972.90