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	$201.93	7.699%	$217.4766	$217.48	$217.50	$217.50
Purchase #2	$186.98	12.607%	$210.5526	$210.55	$210.55	$210.60
Purchase #3	$38.70	3.623%	$40.1021	$40.10	$40.10	$40.10
Purchase #4	$250.40	6.449%	$266.5483	$266.55	$266.55	$266.50
Purchase #5	$106.92	13.112%	$120.9394	$120.94	$120.95	$120.90
Purchase #6	$122.63	7.238%	$131.506	$131.51	$131.50	$131.50
Purchase #7	$60.38	6.814%	$64.4943	$64.49	$64.50	$64.50
7 purchase totals =	$967.94		$1,051.6193	$1,051.62	$1,051.65	$1,051.60