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	$126.65	13.620%	$143.8997	$143.90	$143.90	$143.90
Purchase #2	$159.72	7.498%	$171.6958	$171.70	$171.70	$171.70
Purchase #3	$164.69	9.227%	$179.8859	$179.89	$179.90	$179.90
Purchase #4	$225.82	11.479%	$251.7419	$251.74	$251.75	$251.70
Purchase #5	$59.53	6.327%	$63.2965	$63.30	$63.30	$63.30
Purchase #6	$105.67	13.183%	$119.6005	$119.60	$119.60	$119.60
Purchase #7	$73.33	9.370%	$80.201	$80.20	$80.20	$80.20
7 purchase totals =	$915.41		$1,010.3213	$1,010.33	$1,010.35	$1,010.30