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	$120.95	5.437%	$127.5261	$127.53	$127.55	$127.50
Purchase #2	$110.84	4.639%	$115.9819	$115.98	$116.00	$116.00
Purchase #3	$163.43	3.543%	$169.2203	$169.22	$169.20	$169.20
Purchase #4	$172.77	10.486%	$190.8867	$190.89	$190.90	$190.90
Purchase #5	$34.89	13.813%	$39.7094	$39.71	$39.70	$39.70
Purchase #6	$119.29	5.282%	$125.5909	$125.59	$125.60	$125.60
Purchase #7	$57.62	7.570%	$61.9818	$61.98	$62.00	$62.00
7 purchase totals =	$779.79		$830.8971	$830.90	$830.95	$830.90