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	$207.32	4.550%	$216.7531	$216.75	$216.75	$216.80
Purchase #2	$206.71	10.632%	$228.6874	$228.69	$228.70	$228.70
Purchase #3	$79.85	12.325%	$89.6915	$89.69	$89.70	$89.70
Purchase #4	$144.38	4.518%	$150.9031	$150.90	$150.90	$150.90
Purchase #5	$40.25	13.119%	$45.5304	$45.53	$45.55	$45.50
Purchase #6	$168.87	7.170%	$180.978	$180.98	$181.00	$181.00
Purchase #7	$45.66	12.296%	$51.2744	$51.27	$51.25	$51.30
7 purchase totals =	$893.04		$963.8179	$963.81	$963.85	$963.90