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	$38.72	5.180%	$40.7257	$40.73	$40.75	$40.70
Purchase #2	$183.53	4.477%	$191.7466	$191.75	$191.75	$191.70
Purchase #3	$11.60	6.633%	$12.3694	$12.37	$12.35	$12.40
Purchase #4	$53.26	12.275%	$59.7977	$59.80	$59.80	$59.80
Purchase #5	$183.32	12.484%	$206.2057	$206.21	$206.20	$206.20
Purchase #6	$35.72	7.528%	$38.409	$38.41	$38.40	$38.40
Purchase #7	$206.31	10.666%	$228.315	$228.32	$228.30	$228.30
7 purchase totals =	$712.46		$777.5691	$777.59	$777.55	$777.50