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	$231.92	5.221%	$244.0285	$244.03	$244.05	$244.00
Purchase #2	$89.78	11.197%	$99.8327	$99.83	$99.85	$99.80
Purchase #3	$196.38	11.170%	$218.3156	$218.32	$218.30	$218.30
Purchase #4	$10.75	7.421%	$11.5478	$11.55	$11.55	$11.50
Purchase #5	$219.32	6.818%	$234.2732	$234.27	$234.25	$234.30
Purchase #6	$168.48	13.865%	$191.8398	$191.84	$191.85	$191.80
Purchase #7	$12.68	6.307%	$13.4797	$13.48	$13.50	$13.50
7 purchase totals =	$929.31		$1,013.3173	$1,013.32	$1,013.35	$1,013.20