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	$133.94	9.661%	$146.8799	$146.88	$146.90	$146.90
Purchase #2	$131.72	9.665%	$144.4507	$144.45	$144.45	$144.50
Purchase #3	$158.46	8.216%	$171.4791	$171.48	$171.50	$171.50
Purchase #4	$209.62	7.285%	$224.8908	$224.89	$224.90	$224.90
Purchase #5	$116.76	6.474%	$124.319	$124.32	$124.30	$124.30
Purchase #6	$207.64	9.196%	$226.7346	$226.73	$226.75	$226.70
Purchase #7	$111.79	6.459%	$119.0105	$119.01	$119.00	$119.00
7 purchase totals =	$1,069.93		$1,157.7646	$1,157.76	$1,157.80	$1,157.80