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	$52.84	9.118%	$57.658	$57.66	$57.65	$57.70
Purchase #2	$215.67	3.611%	$223.4578	$223.46	$223.45	$223.50
Purchase #3	$36.63	4.790%	$38.3846	$38.38	$38.40	$38.40
Purchase #4	$102.77	13.252%	$116.3891	$116.39	$116.40	$116.40
Purchase #5	$26.88	8.255%	$29.0989	$29.10	$29.10	$29.10
Purchase #6	$145.53	7.782%	$156.8551	$156.86	$156.85	$156.90
Purchase #7	$77.48	10.533%	$85.641	$85.64	$85.65	$85.60
7 purchase totals =	$657.80		$707.4845	$707.49	$707.50	$707.60