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	$76.79	5.184%	$80.7708	$80.77	$80.75	$80.80
Purchase #2	$179.65	4.779%	$188.2355	$188.24	$188.25	$188.20
Purchase #3	$48.71	5.333%	$51.3077	$51.31	$51.30	$51.30
Purchase #4	$110.25	3.819%	$114.4604	$114.46	$114.45	$114.50
Purchase #5	$245.88	7.609%	$264.589	$264.59	$264.60	$264.60
Purchase #6	$200.93	10.529%	$222.0859	$222.09	$222.10	$222.10
Purchase #7	$83.55	3.315%	$86.3197	$86.32	$86.30	$86.30
7 purchase totals =	$945.76		$1,007.7690	$1,007.78	$1,007.75	$1,007.80