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	$114.37	4.683%	$119.7259	$119.73	$119.75	$119.70
Purchase #2	$249.63	8.112%	$269.88	$269.88	$269.90	$269.90
Purchase #3	$205.44	4.581%	$214.8512	$214.85	$214.85	$214.90
Purchase #4	$185.84	3.257%	$191.8928	$191.89	$191.90	$191.90
Purchase #5	$7.71	12.415%	$8.6672	$8.67	$8.65	$8.70
Purchase #6	$241.35	3.763%	$250.432	$250.43	$250.45	$250.40
Purchase #7	$51.97	13.572%	$59.0234	$59.02	$59.00	$59.00
7 purchase totals =	$1,056.31		$1,114.4725	$1,114.47	$1,114.50	$1,114.50