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	$240.53	10.388%	$265.5163	$265.52	$265.50	$265.50
Purchase #2	$129.86	9.755%	$142.5278	$142.53	$142.55	$142.50
Purchase #3	$198.28	6.685%	$211.535	$211.54	$211.55	$211.50
Purchase #4	$207.38	7.807%	$223.5702	$223.57	$223.55	$223.60
Purchase #5	$59.48	3.600%	$61.6213	$61.62	$61.60	$61.60
Purchase #6	$219.85	8.796%	$239.188	$239.19	$239.20	$239.20
Purchase #7	$248.65	3.730%	$257.9246	$257.92	$257.90	$257.90
7 purchase totals =	$1,304.03		$1,401.8832	$1,401.89	$1,401.85	$1,401.80