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	$202.32	3.728%	$209.8625	$209.86	$209.85	$209.90
Purchase #2	$83.99	6.602%	$89.535	$89.54	$89.55	$89.50
Purchase #3	$99.84	9.109%	$108.9344	$108.93	$108.95	$108.90
Purchase #4	$99.72	7.119%	$106.8191	$106.82	$106.80	$106.80
Purchase #5	$215.91	3.467%	$223.3956	$223.40	$223.40	$223.40
Purchase #6	$125.76	5.304%	$132.4303	$132.43	$132.45	$132.40
Purchase #7	$11.35	10.576%	$12.5504	$12.55	$12.55	$12.60
7 purchase totals =	$838.89		$883.5273	$883.53	$883.55	$883.50