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	$70.61	3.740%	$73.2508	$73.25	$73.25	$73.30
Purchase #2	$92.55	4.703%	$96.9026	$96.90	$96.90	$96.90
Purchase #3	$31.39	4.656%	$32.8515	$32.85	$32.85	$32.90
Purchase #4	$118.55	13.543%	$134.6052	$134.61	$134.60	$134.60
Purchase #5	$35.43	12.495%	$39.857	$39.86	$39.85	$39.90
Purchase #6	$173.88	7.759%	$187.3713	$187.37	$187.35	$187.40
Purchase #7	$218.26	6.108%	$231.5913	$231.59	$231.60	$231.60
7 purchase totals =	$740.67		$796.4297	$796.43	$796.40	$796.60