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	$58.81	8.564%	$63.8465	$63.85	$63.85	$63.80
Purchase #2	$195.89	3.331%	$202.4151	$202.42	$202.40	$202.40
Purchase #3	$207.50	4.250%	$216.3188	$216.32	$216.30	$216.30
Purchase #4	$45.36	12.489%	$51.025	$51.03	$51.05	$51.00
Purchase #5	$114.72	12.332%	$128.8673	$128.87	$128.85	$128.90
Purchase #6	$209.73	3.273%	$216.5945	$216.59	$216.60	$216.60
Purchase #7	$133.76	4.563%	$139.8635	$139.86	$139.85	$139.90
7 purchase totals =	$965.77		$1,018.9307	$1,018.94	$1,018.90	$1,018.90