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	$202.51	3.731%	$210.0656	$210.07	$210.05	$210.10
Purchase #2	$181.64	8.203%	$196.5399	$196.54	$196.55	$196.50
Purchase #3	$196.72	13.113%	$222.5159	$222.52	$222.50	$222.50
Purchase #4	$157.91	13.797%	$179.6968	$179.70	$179.70	$179.70
Purchase #5	$118.84	3.153%	$122.587	$122.59	$122.60	$122.60
Purchase #6	$122.46	7.295%	$131.3935	$131.39	$131.40	$131.40
Purchase #7	$77.87	3.429%	$80.5402	$80.54	$80.55	$80.50
7 purchase totals =	$1,057.95		$1,143.3389	$1,143.35	$1,143.35	$1,143.30