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	$106.58	9.616%	$116.8287	$116.83	$116.85	$116.80
Purchase #2	$112.73	13.519%	$127.97	$127.97	$127.95	$128.00
Purchase #3	$85.59	5.736%	$90.4994	$90.50	$90.50	$90.50
Purchase #4	$222.35	8.275%	$240.7495	$240.75	$240.75	$240.70
Purchase #5	$163.67	4.872%	$171.644	$171.64	$171.65	$171.60
Purchase #6	$158.41	9.731%	$173.8249	$173.82	$173.80	$173.80
Purchase #7	$215.87	3.691%	$223.8378	$223.84	$223.85	$223.80
7 purchase totals =	$1,065.20		$1,145.3543	$1,145.35	$1,145.35	$1,145.20