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	$231.76	10.460%	$256.0021	$256.00	$256.00	$256.00
Purchase #2	$184.90	3.774%	$191.8781	$191.88	$191.90	$191.90
Purchase #3	$60.70	6.687%	$64.759	$64.76	$64.75	$64.80
Purchase #4	$223.82	6.748%	$238.9234	$238.92	$238.90	$238.90
Purchase #5	$89.48	10.482%	$98.8593	$98.86	$98.85	$98.90
Purchase #6	$94.57	8.774%	$102.8676	$102.87	$102.85	$102.90
Purchase #7	$53.39	8.392%	$57.8705	$57.87	$57.85	$57.90
7 purchase totals =	$938.62		$1,011.1600	$1,011.16	$1,011.10	$1,011.30