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	$248.98	7.241%	$267.0086	$267.01	$267.00	$267.00
Purchase #2	$111.76	7.841%	$120.5231	$120.52	$120.50	$120.50
Purchase #3	$89.90	10.748%	$99.5625	$99.56	$99.55	$99.60
Purchase #4	$48.63	10.777%	$53.8709	$53.87	$53.85	$53.90
Purchase #5	$191.98	8.158%	$207.6417	$207.64	$207.65	$207.60
Purchase #6	$215.38	3.687%	$223.3211	$223.32	$223.30	$223.30
Purchase #7	$92.27	6.221%	$98.0101	$98.01	$98.00	$98.00
7 purchase totals =	$998.90		$1,069.9380	$1,069.93	$1,069.85	$1,069.90