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	$151.52	3.555%	$156.9065	$156.91	$156.90	$156.90
Purchase #2	$31.78	7.159%	$34.0551	$34.06	$34.05	$34.10
Purchase #3	$76.25	5.127%	$80.1593	$80.16	$80.15	$80.20
Purchase #4	$179.79	6.751%	$191.9276	$191.93	$191.95	$191.90
Purchase #5	$167.32	13.872%	$190.5306	$190.53	$190.55	$190.50
Purchase #6	$132.40	3.749%	$137.3637	$137.36	$137.35	$137.40
Purchase #7	$18.50	10.240%	$20.3944	$20.39	$20.40	$20.40
7 purchase totals =	$757.56		$811.3372	$811.34	$811.35	$811.40