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	$85.69	4.211%	$89.2984	$89.30	$89.30	$89.30
Purchase #2	$67.25	3.824%	$69.8216	$69.82	$69.80	$69.80
Purchase #3	$126.39	13.114%	$142.9648	$142.96	$142.95	$143.00
Purchase #4	$58.43	12.641%	$65.8161	$65.82	$65.80	$65.80
Purchase #5	$200.67	8.676%	$218.0801	$218.08	$218.10	$218.10
Purchase #6	$85.52	11.402%	$95.271	$95.27	$95.25	$95.30
Purchase #7	$101.65	12.393%	$114.2475	$114.25	$114.25	$114.20
7 purchase totals =	$725.60		$795.4995	$795.50	$795.45	$795.50