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	$26.83	6.448%	$28.56	$28.56	$28.55	$28.60
Purchase #2	$222.67	3.555%	$230.5859	$230.59	$230.60	$230.60
Purchase #3	$214.78	3.735%	$222.802	$222.80	$222.80	$222.80
Purchase #4	$31.30	12.427%	$35.1897	$35.19	$35.20	$35.20
Purchase #5	$182.97	9.754%	$200.8169	$200.82	$200.80	$200.80
Purchase #6	$66.80	13.438%	$75.7766	$75.78	$75.80	$75.80
Purchase #7	$218.76	3.258%	$225.8872	$225.89	$225.90	$225.90
7 purchase totals =	$964.11		$1,019.6183	$1,019.63	$1,019.65	$1,019.70