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	$226.57	3.447%	$234.3799	$234.38	$234.40	$234.40
Purchase #2	$189.75	12.817%	$214.0703	$214.07	$214.05	$214.10
Purchase #3	$101.32	9.185%	$110.6262	$110.63	$110.65	$110.60
Purchase #4	$81.90	9.765%	$89.8975	$89.90	$89.90	$89.90
Purchase #5	$118.61	4.284%	$123.6913	$123.69	$123.70	$123.70
Purchase #6	$151.28	11.537%	$168.7332	$168.73	$168.75	$168.70
Purchase #7	$163.61	5.533%	$172.6625	$172.66	$172.65	$172.70
7 purchase totals =	$1,033.04		$1,114.0609	$1,114.06	$1,114.10	$1,114.10